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Kishnani PS, Seefried L, Dahir KM, Martos-Moreno GÁ, Linglart A, Petryk A, Mowrey WR, Fang S, Ozono K, Högler W, Rockman-Greenberg C. New insights into the landscape of ALPL gene variants in patients with hypophosphatasia from the Global HPP Registry. Am J Med Genet A 2024:e63781. [PMID: 38884565 DOI: 10.1002/ajmg.a.63781] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2024] [Revised: 04/29/2024] [Accepted: 05/20/2024] [Indexed: 06/18/2024]
Abstract
Hypophosphatasia (HPP) is a rare, inherited metabolic disease characterized by low tissue-nonspecific alkaline phosphatase activity due to ALPL gene variants. We describe ALPL variants from the observational, prospective, multinational Global HPP Registry. Inclusion in the analysis required a diagnosis of HPP, low serum ALP activity, and ≥1 ALPL variant. Of 1176 patients enrolled as of September 2022, 814 met inclusion criteria in Europe (48.9%), North America (36.7%), Japan (10.2%), Australia (2.6%), and elsewhere (1.6%). Most patients (74.7%) had 1 ALPL variant; 25.3% had ≥2 variants. Nearly all patients (95.6%) had known disease-causing variants; 4.4% had variants of uncertain significance. Disease-causing variants were predominantly missense (770/1556 alleles). The most common variants were c.571G>A (102/1628 alleles), c.1250A>G (66/1628 alleles), and c.1559del (61/1628 alleles). Variant profiles were generally consistent, except in Japan, where a higher proportion of patients (68.7%) had ≥2 ALPL variants, likely because more had disease onset before age 6 months (53.0% vs. 10.1%-23.1% elsewhere). Frameshift mutations (61/164 alleles) and inframe deletions (7/164 alleles) were more common in Japan. Twenty-three novel variants were discovered, each in a single geographic region, predominantly Europe. Analyses confirmed previously known ALPL variants, identified novel variants, and characterized geographic variation in frequency and type of ALPL variants in a large population.
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Affiliation(s)
| | | | - Kathryn M Dahir
- Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Gabriel Ángel Martos-Moreno
- Hospital Infantil Universitario Niño Jesús, IIS La Princesa, Universidad Autónoma de Madrid, CIBERobn, ISCIII, Madrid, Spain
| | - Agnès Linglart
- Paris-Saclay University, AP-HP and INSERM, Paris, France
| | - Anna Petryk
- Alexion, AstraZeneca Rare Disease, Boston, Massachusetts, USA
| | | | - Shona Fang
- Alexion, AstraZeneca Rare Disease, Boston, Massachusetts, USA
| | - Keiichi Ozono
- Iseikai International General Hospital, Kita Ward, Osaka, Japan
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Brandi ML, Khan AA, Rush ET, Ali DS, Al-Alwani H, Almonaei K, Alsarraf F, Bacrot S, Dahir KM, Dandurand K, Deal C, Ferrari SL, Giusti F, Guyatt G, Hatcher E, Ing SW, Javaid MK, Khan S, Kocijan R, Lewiecki EM, Linglart A, M'Hiri I, Marini F, Nunes ME, Rockman-Greenberg C, Seefried L, Simmons JH, Starling SR, Ward LM, Yao L, Brignardello-Petersen R, Roux C. The challenge of hypophosphatasia diagnosis in adults: results from the HPP International Working Group Literature Surveillance. Osteoporos Int 2024; 35:439-449. [PMID: 37982856 DOI: 10.1007/s00198-023-06859-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/06/2023] [Accepted: 07/10/2023] [Indexed: 11/21/2023]
Abstract
Hypophosphatasia (HPP) is an inborn error of metabolism caused by reduced or absent activity of the tissue non-specific alkaline phosphatase (TNSALP) enzyme, resulting from pathogenic variants in the ALPL gene. Clinical presentation of HPP is highly variable, including lethal and severe forms in neonates and infants, a benign perinatal form, mild forms manifesting in adulthood, and odonto-HPP. Diagnosis of HPP remains a challenge in adults, as signs and symptoms may be mild and non-specific. Disease presentation varies widely; there are no universal signs or symptoms, and the disease often remains underdiagnosed or misdiagnosed, particularly by clinicians who are not familiar with this rare disorder. The absence of diagnosis or a delayed diagnosis may prevent optimal management for patients with this condition. Formal guidelines for the diagnosis of adults with HPP do not exist, complicating efforts for consistent diagnosis. To address this issue, the HPP International Working Group selected 119 papers that explicitly address the diagnosis of HPP in adults through a Medline, Medline In-Process, and Embase search for the terms "hypophosphatasia" and "HPP," and evaluated the pooled prevalence of 17 diagnostic characteristics, initially selected by a group of HPP clinical experts, in eligible studies and in patients included in these studies. Six diagnostic findings showed a pooled prevalence value over 50% and were considered for inclusion as major diagnostic criteria. Based on these results and according to discussion and consideration among members of the Working Group, we finally defined four major diagnostic criteria and five minor diagnostic criteria for HPP in adults. Authors suggested the integrated use of the identified major and minor diagnostic criteria, which either includes two major criteria, or one major criterion and two minor criteria, for the diagnosis of HPP in adults.
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Affiliation(s)
- Maria Luisa Brandi
- F.I.R.M.O. Italian Foundation for the Research On Bone Diseases, Florence, Italy.
- Donatello Bone Clinic, Villa Donatello Hospital, Florence, Italy.
| | - Aliya A Khan
- Division of Endocrinology and Metabolism, McMaster University, Hamilton, Canada
| | - Eric T Rush
- Division of Clinical Genetics, Children's Mercy Kansas City and Department of Pediatrics, University of Missouri-Kansas City School of Medicine, Kansas City, MO, USA
- Division of Endocrinology, Metabolism, Osteoporosis, and Genetics, Department of Internal Medicine, University of Kansas School of Medicine, Kansas City, KS, USA
| | - Dalal S Ali
- Division of Endocrinology and Metabolism, McMaster University, Hamilton, Canada
| | - Hatim Al-Alwani
- Division of Endocrinology and Metabolism, McMaster University, Hamilton, Canada
| | - Khulod Almonaei
- Division of Endocrinology and Metabolism, McMaster University, Hamilton, Canada
| | - Farah Alsarraf
- Division of Endocrinology and Metabolism, McMaster University, Hamilton, Canada
| | - Severine Bacrot
- Department of Genetics, Centre Hospitalier de Versailles, Hôpital André Mignot, Versailles, France
| | - Kathryn M Dahir
- Division of Endocrinology and Metabolism, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Karel Dandurand
- Department of Medicine, Endocrinology and Metabolism, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Chad Deal
- Center for Osteoporosis and Metabolic Bone Disease, Department of Rheumatology, The Cleveland Clinic Foundation, Cleveland, OH, USA
| | - Serge Livio Ferrari
- Division of Bone Diseases, Department of Internal Medicine Specialties, Geneva University Hospitals and Faculty of Medicine, Geneva, Switzerland
| | - Francesca Giusti
- Donatello Bone Clinic, Villa Donatello Hospital, Florence, Italy
| | - Gordon Guyatt
- Department of Health Research Methods, Evidence, and Impact, McMaster University, Hamilton, ON, Canada
| | - Erin Hatcher
- Neuromuscular Clinic, McMaster University Medical Centre, Hamilton Health Sciences, Hamilton, ON, Canada
| | - Steven W Ing
- Division of Endocrinology, Diabetes, & Metabolism, Ohio State University Wexner Medical Center, Columbus, OH, USA
| | - Muhammad Kassim Javaid
- Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, UK
| | - Sarah Khan
- Bone Research and Education Centre, Oakville, ON, Canada
| | - Roland Kocijan
- Trauma Centre Meidling, Ludwig Boltzmann Institute of Osteology at Hanusch Hospital of OEGK and AUVA, 1St Medical Department Hanusch Hospital, 1140, Vienna, Austria
| | - E Michael Lewiecki
- New Mexico Clinical Research & Osteoporosis Center, Albuquerque, NM, USA
| | - Agnes Linglart
- APHP, Bicêtre Paris-Sud, University Paris Sud, Paris-Saclay, Le Kremlin Bicêtre, Paris, France
| | - Iman M'Hiri
- Bone Research and Education Centre, Oakville, ON, Canada
| | - Francesca Marini
- F.I.R.M.O. Italian Foundation for the Research On Bone Diseases, Florence, Italy
| | - Mark E Nunes
- Division of Medical Genetics and Metabolism, Valley Children's HealthCare, Madera, CA, USA
| | | | - Lothar Seefried
- Musculoskeletal Center Würzburg, University of Würzburg, Würzburg, Germany
| | - Jill H Simmons
- Division of Endocrinology and Metabolism, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Susan R Starling
- Division of Clinical Genetics, Children's Mercy Kansas City and Department of Pediatrics, University of Missouri-Kansas City School of Medicine, Kansas City, MO, USA
| | - Leanne M Ward
- Department of Pediatrics, Children's Hospital of Eastern Ontario, University of Ottawa, Ottawa, ON, Canada
| | - Liang Yao
- Department of Health Research Methods, Evidence, and Impact, McMaster University, Hamilton, ON, Canada
| | | | - Christian Roux
- INSERM CRESS UMR 1153, Paris, France
- Université Paris-Cité, Department of Rheumatology, APHP-Centre, Cochin Hospital, Paris, France
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Martínez-Heredia L, Muñoz-Torres M, Sanabria-de la Torre R, Jiménez-Ortas Á, Andújar-Vera F, González-Cejudo T, Contreras-Bolívar V, González-Salvatierra S, Gómez-Vida JM, García-Fontana C, García-Fontana B. Systemic effects of hypophosphatasia characterization of two novel variants in the ALPL gene. Front Endocrinol (Lausanne) 2024; 14:1320516. [PMID: 38234425 PMCID: PMC10792043 DOI: 10.3389/fendo.2023.1320516] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/12/2023] [Accepted: 12/04/2023] [Indexed: 01/19/2024] Open
Abstract
Introduction Hypophosphatasia (HPP) is an inborn metabolic error caused by mutations in the ALPL gene encoding tissue non-specific alkaline phosphatase (TNSALP) and leading to decreased alkaline phosphatase (ALP) activity. Although the main characteristic of this disease is bone involvement, it presents a great genetic and clinical variability, which makes it a systemic disease. Methods Patients were recruited based on biochemical assessments. Diagnosis was made by measuring serum ALP and pyridoxal 5-phosphate levels and finally by Sanger sequencing of the ALPL gene from peripheral blood mononuclear cells. Characterization of the new variants was performed by transfection of the variants into HEK293T cells, where ALP activity and cellular localization were measured by flow cytometry. The dominant negative effect was analyzed by co-transfection of each variant with the wild-type gene, measuring ALP activity and analyzing cellular localization by flow cytometry. Results Two previously undescribed variants were found in the ALPL gene: leucine 6 to serine missense mutation (c.17T>C, L6S) affecting the signal peptide and threonine 167 deletion (c.498_500delCAC, T167del) affecting the vicinity of the active site. These mutations lead mainly to non-pathognomonic symptoms of HPP. Structural prediction and modeling tools indicated the affected residues as critical residues with important roles in protein structure and function. In vitro results demonstrated low TNSALP activity and a dominant negative effect in both mutations. The results of the characterization of these variants suggest that the pleiotropic role of TNSALP could be involved in the systemic effects observed in these patients highlighting digestive and autoimmune disorders associated with TNSALP dysfunction. Conclusions The two new mutations have been classified as pathogenic. At the clinical level, this study suggests that both mutations not only lead to pathognomonic symptoms of the disease, but may also play a role at the systemic level.
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Affiliation(s)
| | - Manuel Muñoz-Torres
- Instituto de Investigación Biosanitaria de Granada, Granada, Spain
- Endocrinology and Nutrition Unit, University Hospital Clínico San Cecilio, Granada, Spain
- Department of Medicine, University of Granada, Granada, Spain
- Biomedical Research Network in Fragility and Healthy Aging (CIBERFES), Instituto de Salud Carlos III, Madrid, Spain
| | - Raquel Sanabria-de la Torre
- Instituto de Investigación Biosanitaria de Granada, Granada, Spain
- Department of Biochemistry, Molecular Biology III and Immunology, University of Granada, Granada, Spain
| | - Ángela Jiménez-Ortas
- Instituto de Investigación Biosanitaria de Granada, Granada, Spain
- Department of Biochemistry and Molecular Biology II, University of Granada, Granada, Spain
| | - Francisco Andújar-Vera
- Department of Computer Science and Artificial Intelligence, University of Granada, Granada, Spain
- Andalusian Research Institute in Data Science and Computational Intelligence (DaSCI Institute), Granada, Spain
- Bioinformatic Service, Instituto de Investigación Biosanitaria de Granada, Granada, Spain
| | - Trinidad González-Cejudo
- Instituto de Investigación Biosanitaria de Granada, Granada, Spain
- Clinical Analysis Unit, University Hospital Clínico San Cecilio, Granada, Spain
| | | | - Sheila González-Salvatierra
- Instituto de Investigación Biosanitaria de Granada, Granada, Spain
- Endocrinology and Nutrition Unit, University Hospital Clínico San Cecilio, Granada, Spain
- Department of Medicine, University of Granada, Granada, Spain
| | | | - Cristina García-Fontana
- Instituto de Investigación Biosanitaria de Granada, Granada, Spain
- Endocrinology and Nutrition Unit, University Hospital Clínico San Cecilio, Granada, Spain
- Biomedical Research Network in Fragility and Healthy Aging (CIBERFES), Instituto de Salud Carlos III, Madrid, Spain
| | - Beatriz García-Fontana
- Instituto de Investigación Biosanitaria de Granada, Granada, Spain
- Endocrinology and Nutrition Unit, University Hospital Clínico San Cecilio, Granada, Spain
- Biomedical Research Network in Fragility and Healthy Aging (CIBERFES), Instituto de Salud Carlos III, Madrid, Spain
- Department of Cell Biology, University of Granada, Granada, Spain
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Rush E, Brandi ML, Khan A, Ali DS, Al-Alwani H, Almonaei K, Alsarraf F, Bacrot S, Dahir KM, Dandurand K, Deal C, Ferrari SL, Giusti F, Guyatt G, Hatcher E, Ing SW, Javaid MK, Khan S, Kocijan R, Lewiecki EM, Linglart A, M'Hiri I, Marini F, Nunes ME, Rockman-Greenberg C, Roux C, Seefried L, Starling SR, Ward L, Yao L, Brignardello-Petersen R, Simmons JH. Proposed diagnostic criteria for the diagnosis of hypophosphatasia in children and adolescents: results from the HPP International Working Group. Osteoporos Int 2024; 35:1-10. [PMID: 37982855 PMCID: PMC10786745 DOI: 10.1007/s00198-023-06843-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/30/2022] [Accepted: 06/23/2023] [Indexed: 11/21/2023]
Abstract
Hypophosphatasia (HPP) is a rare inborn error of metabolism that presents variably in both age of onset and severity. HPP is caused by pathogenic variants in the ALPL gene, resulting in low activity of tissue nonspecific alkaline phosphatase (TNSALP). Patients with HPP tend have a similar pattern of elevation of natural substrates that can be used to aid in diagnosis. No formal diagnostic guidelines currently exist for the diagnosis of this condition in children, adolescents, or adults. The International HPP Working Group is a comprised of a multidisciplinary team of experts from Europe and North America who have expertise in the diagnosis and management of patients with HPP. This group reviewed 93 papers through a Medline, Medline In-Process, and Embase search for the terms "HPP" and "hypophosphatasia" between 2005 and 2020 and that explicitly address either the diagnosis of HPP in children, clinical manifestations of HPP in children, or both. Two reviewers independently evaluated each full-text publication for eligibility and studies were included if they were narrative reviews or case series/reports that concerned diagnosis of pediatric HPP or included clinical aspects of patients diagnosed with HPP. This review focused on 15 initial clinical manifestations that were selected by a group of clinical experts.The highest agreement in included literature was for pathogenic or likely pathogenic ALPL variant, elevation of natural substrates, and early loss of primary teeth. The highest prevalence was similar, including these same three parameters and including decreased bone mineral density. Additional parameters had less agreement and were less prevalent. These were organized into three major and six minor criteria, with diagnosis of HPP being made when two major or one major and two minor criteria are present.
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Affiliation(s)
- Eric Rush
- Division of Clinical Genetics, Children's Mercy Kansas City, 2401 Gillham Road, Kansas City, MO, USA.
- Department of Pediatrics, University of Missouri - Kansas City School of Medicine, 2401 Gillham Road, Kansas City, MO, USA.
- Division of Endocrinology, Metabolism, Osteoporosis, and Genetics, Department of Internal Medicine, University of Kansas School of Medicine, Kansas City, KS, USA.
| | - Maria Luisa Brandi
- F.I.R.M.O. Italian Foundation for the Research on Bone Diseases, Florence, Italy
- Donatello Bone Clinic, Villa Donatello Hospital, Florence, Italy
| | - Aliya Khan
- Division of Endocrinology and Metabolism, McMaster University, Hamilton, Canada
| | - Dalal S Ali
- Division of Endocrinology and Metabolism, McMaster University, Hamilton, Canada
| | - Hatim Al-Alwani
- Division of Endocrinology and Metabolism, McMaster University, Hamilton, Canada
| | - Khulod Almonaei
- Division of Endocrinology and Metabolism, McMaster University, Hamilton, Canada
| | - Farah Alsarraf
- Division of Endocrinology and Metabolism, McMaster University, Hamilton, Canada
| | - Severine Bacrot
- Department of Genetics, Centre Hospitalier de Versailles, Hôpital André Mignot, Versailles, France
| | - Kathryn M Dahir
- Division of Endocrinology and Metabolism, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Karel Dandurand
- Department of Medicine, Endocrinology and Metabolism, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Chad Deal
- Center for Osteoporosis and Metabolic Bone Disease, Department of Rheumatology, The Cleveland Clinic Foundation, Cleveland, OH, USA
| | - Serge Livio Ferrari
- Division of Bone Diseases, Department of Internal Medicine Specialties, Geneva University Hospitals and Faculty of Medicine, Geneva, Switzerland
| | - Francesca Giusti
- Donatello Bone Clinic, Villa Donatello Hospital, Florence, Italy
| | - Gordon Guyatt
- Department of Health Research Methods, Evidence, and Impact, McMaster University, Hamilton, Canada
| | - Erin Hatcher
- Neuromuscular Clinic, McMaster University Medical Centre, Hamilton Health Sciences, Hamilton, Canada
| | - Steven W Ing
- Division of Endocrinology, Diabetes, & Metabolism, Ohio State University Wexner Medical Center, Columbus, USA
| | - Muhammad Kassim Javaid
- Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, UK
| | - Sarah Khan
- Bone Research and Education Centre, Oakville, ON, Canada
| | - Roland Kocijan
- 1st Medical Department, Ludwig Boltzmann Institute of Osteology at Hanusch Hospital of OEGK and AUVA, Trauma Centre Meidling, Hanusch Hospital, 1140, Vienna, Austria
| | - E Michael Lewiecki
- New Mexico Clinical Research & Osteoporosis Center, Albuquerque, NM, USA
| | - Agnes Linglart
- APHP, Bicêtre Paris-Sud, University Paris Sud, Paris-Saclay, Le Kremlin Bicêtre, Paris, France
| | - Iman M'Hiri
- Bone Research and Education Centre, Oakville, ON, Canada
| | - Francesca Marini
- F.I.R.M.O. Italian Foundation for the Research on Bone Diseases, Florence, Italy
| | - Mark E Nunes
- Division of Medical Genetics and Metabolism, Valley Children's HealthCare, Madera, CA, USA
| | | | - Christian Roux
- Rheumatology Department, Hospital Pasteur 2 CHU, 06000, Nice, France
- Inserm, CNRS, iBV, Université Côte d'Azur, 06000, Nice, France
| | - Lothar Seefried
- Musculoskeletal Center Wuerzburg, University of Wuerzburg, Wuerzburg, Germany
| | - Susan R Starling
- Division of Clinical Genetics, Children's Mercy Kansas City, 2401 Gillham Road, Kansas City, MO, USA
| | - Leanne Ward
- Children's Hospital of Eastern Ontario, Department of Pediatrics, University of Ottawa, Ottawa, Ontario, Canada
| | - Liang Yao
- Department of Health Research Methods, Evidence, and Impact, McMaster University, Hamilton, Canada
| | | | - Jill H Simmons
- Division of Endocrinology and Metabolism, Vanderbilt University Medical Center, Nashville, TN, USA
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Farman MR, Rehder C, Malli T, Rockman-Greenberg C, Dahir K, Martos-Moreno GÁ, Linglart A, Ozono K, Seefried L, Del Angel G, Webersinke G, Barbazza F, John LK, Delana Mudiyanselage SMA, Högler F, Nading EB, Huggins E, Rush ET, El-Gazzar A, Kishnani PS, Högler W. The Global ALPL gene variant classification project: Dedicated to deciphering variants. Bone 2024; 178:116947. [PMID: 37898381 DOI: 10.1016/j.bone.2023.116947] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/04/2023] [Revised: 10/15/2023] [Accepted: 10/17/2023] [Indexed: 10/30/2023]
Abstract
BACKGROUND Hypophosphatasia (HPP) is an inherited multisystem disorder predominantly affecting the mineralization of bones and teeth. HPP is caused by pathogenic variants in ALPL, which encodes tissue non-specific alkaline phosphatase (TNSALP). Variants of uncertain significance (VUS) cause diagnostic delay and uncertainty amongst patients and health care providers. RESULTS The ALPL gene variant database (https://alplmutationdatabase.jku.at/) is an open-access archive for interpretation of the clinical significance of variants reported in ALPL. The database contains coding and non-coding variants, including single nucleotide variants, insertions/deletions and structural variants affecting coding or non-coding sequences of ALPL. Each variant in the database is displayed with details explaining the corresponding pathogenicity, and all reported genotypes and phenotypes, including references. In 2021, the ALPL gene variant classification project was established to reclassify VUS and continuously assess and update genetic, phenotypic, and functional variant information in the database. For this purpose, the database provides a unique submission system for clinicians, geneticists, genetic counselors, and researchers to submit VUS within ALPL for classification. An international, multidisciplinary consortium of HPP experts has been established to reclassify the submitted VUS using a multi-step process adhering to the stringent ACMG/AMP variant classification guidelines. These steps include a clinical phenotype assessment, deep literature research including artificial intelligence technology, molecular genetic assessment, and in-vitro functional testing of variants in a co-transfection model to measure ALP residual activity. CONCLUSION This classification project and the ALPL gene variant database will serve the global medical community, widen the genotypic and phenotypic HPP spectrum by reporting and characterizing new ALPL variants based on ACMG/AMP criteria and thus facilitate improved genetic counseling and medical decision-making for affected patients and families. The project may also serve as a gold standard framework for multidisciplinary collaboration for variant interpretation in other rare diseases.
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Affiliation(s)
- Mariam R Farman
- Department of Paediatrics and Adolescent Medicine, Johannes Kepler University Linz, Linz, Austria
| | - Catherine Rehder
- Duke University Medical Center, Department of Pathology, Durham, USA
| | - Theodora Malli
- Laboratory for Molecular Genetic Diagnostics, Ordensklinikum Linz, Linz, Austria
| | - Cheryl Rockman-Greenberg
- Department of Pediatrics and Child Health Max Rady College of Medicine, Rady Faculty of Health Sciences, Winnipeg, Canada
| | - Kathryn Dahir
- Vanderbilt University Medical Center, Program for Metabolic Bone Disorders, Nashville, TN, USA
| | - Gabriel Ángel Martos-Moreno
- Departments of Pediatrics & Pediatric Endocrinology, Hospital Infantil Universitario Niño Jesús, Madrid, Spain
- Department of Pediatrics, Universidad Autónoma de Madrid, Madrid, Spain
- CIBER Fisiopatología de la Obesidad y Nutrición, ISCIII, Madrid, Spain
| | - Agnès Linglart
- AP-HP, Paris Saclay University, INSERM, Bicêtre Paris Saclay hospital, Le Kremlin-Bicêtre, France
| | - Keiichi Ozono
- Department of Pediatrics, Osaka University Graduate School of Medicine, Osaka, Japan
| | | | | | - Gerald Webersinke
- Laboratory for Molecular Genetic Diagnostics, Ordensklinikum Linz, Linz, Austria
| | - Francesca Barbazza
- Department of Paediatrics and Adolescent Medicine, Johannes Kepler University Linz, Linz, Austria
| | - Lisa K John
- Department of Paediatrics and Adolescent Medicine, Johannes Kepler University Linz, Linz, Austria
| | | | - Florian Högler
- Department of Paediatrics and Adolescent Medicine, Johannes Kepler University Linz, Linz, Austria
| | - Erica Burner Nading
- Duke University Medical Center, Division of Medical Genetics, Department of Pediatrics, Durham, USA
| | - Erin Huggins
- Duke University Medical Center, Division of Medical Genetics, Department of Pediatrics, Durham, USA
| | - Eric T Rush
- Division of Clinical Genetics, Children's Mercy Hospital Kansas City, Kansas City, MO, USA
- Department of Internal Medicine, University of Kansas School of Medicine, Kansas City, KS, USA
- Department of Pediatrics, University of Missouri – Kansas City School of Medicine, Kansas City, MO, USA
| | - Ahmed El-Gazzar
- Department of Paediatrics and Adolescent Medicine, Johannes Kepler University Linz, Linz, Austria
| | - Priya S Kishnani
- Duke University Medical Center, Division of Medical Genetics, Department of Pediatrics, Durham, USA
| | - Wolfgang Högler
- Department of Paediatrics and Adolescent Medicine, Johannes Kepler University Linz, Linz, Austria
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6
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Kim SM, Korkmaz F, Sims S, Ryu V, Yuen T, Zaidi M. Musculoskeletal and neurocognitive clinical significance of adult hypophosphatasia. Osteoporos Sarcopenia 2023; 9:115-120. [PMID: 38374822 PMCID: PMC10874721 DOI: 10.1016/j.afos.2023.12.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/07/2023] [Revised: 12/03/2023] [Accepted: 12/12/2023] [Indexed: 02/21/2024] Open
Abstract
Hypophosphatasia (HPP), also called Rathbun disease, is a rare genetic disorder that is caused by the loss-of-function mutation in the ALPL gene encoding tissue non-specific alkaline phosphatase. Doctor Rathbun first described the case of a 3-week-old infant who presented with severe osteopenia, rickets, and multiple radiographic fractures, and died shortly after of epileptic seizure and respiratory distress. The term "hypophosphatasia" was coined as the patients' alkaline phosphatase levels were significantly low. Since then, our understanding of HPP has evolved, and now we appreciate causative genetic mutation and the broad spectrum of clinical presentation depending on the age of onset, severity, and skeletal involvement: perinatal, infantile, childhood, adult and odontohypophosphatasia. The new development of enzyme replacement with asfostase alfa has saved the lives of severe form of hypophosphatasia. However, it is still unclear and remains challenging how to manage adult HPP that often presents with mild and non-specific symptoms such as muscle pain, joint stiffness, fatigue, anxiety, or low bone mass, which are common in the general population and not necessarily attributed to HPP. In this review, we will present 3 unique cases of adult HPP and discuss the pathophysiology, clinical presentation particularly neuromuscular and neurocognitive symptoms and management of adult HPP.
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Affiliation(s)
- Se-Min Kim
- Center for Translational Medicine and Pharmacological Science, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Funda Korkmaz
- Center for Translational Medicine and Pharmacological Science, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Steve Sims
- Center for Translational Medicine and Pharmacological Science, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Vitaly Ryu
- Center for Translational Medicine and Pharmacological Science, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Tony Yuen
- Center for Translational Medicine and Pharmacological Science, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Mone Zaidi
- Center for Translational Medicine and Pharmacological Science, Icahn School of Medicine at Mount Sinai, New York, NY, USA
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7
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Fratzl-Zelman N, Linglart A, Bin K, Rauch F, Blouin S, Coutant R, Donzeau A. Combination of osteogenesis imperfecta and hypophosphatasia in three children with multiple fractures, low bone mass and severe osteomalacia, a challenge for therapeutic management. Eur J Med Genet 2023; 66:104856. [PMID: 37758163 DOI: 10.1016/j.ejmg.2023.104856] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Revised: 09/05/2023] [Accepted: 09/24/2023] [Indexed: 10/03/2023]
Abstract
Osteogenesis imperfecta (OI) and hypophosphatasia (HPP) are rare skeletal disorders caused by mutations in the genes encoding collagen type I (COL1A, COL1A2) and tissue-non-specific isoenzyme of alkaline phosphatase (ALPL), respectively. Both conditions result in skeletal deformities and bone fragility although bone tissue abnormalities differ considerably. Children with OI have low bone mass and hypermineralized matrix, whereas HPP children develop rickets and osteomalacia. We report a family, father and three children, affected with growth retardation, low bone mass and recurrent fractures. None of them had rickets, blue sclera or dentinogenesis imperfecta. ALP serum levels were low and genetics revealed in the four probands heterozygous pathogenic mutations in COL1A2 c.838G > A (p.Gly280Ser) and in ALPL c.1333T > C (p.Ser445Pro). After multidisciplinary meeting, a diagnostic transiliac bone biopsy was indicated for each sibling for therapeutic decision. Bone histology and histomorphometry, as compared to reference values of children with OI type I as well as, to a control pediatric patient harboring the same COL1A2 mutation, revealed similarly decreased trabecular bone volume, increased osteocyte lacunae, but additionally severe osteomalacia. Quantitative backscattered electron imaging demonstrated that bone matrix mineralization was not as decreased as expected for osteomalacia. In summary, we observed within each biopsy samples classical features of OI and classical features of HPP. The apparent nearly normal bone mineralization density distribution results presumably from divergent effects of OI and HPP on matrix mineralization. A combination therapy was initiated with ALP enzyme-replacement and one month later with bisphosphonates. The ongoing treatment led to improved skeletal growth, increased BMD and markedly reduced fracture incidence.
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Affiliation(s)
- Nadja Fratzl-Zelman
- Ludwig Boltzmann Institute of Osteology at Hanusch Hospital of OEGK and AUVA Trauma Centre Meidling, 1st Med. Department Hanusch Hospital, Vienna, Austria; Vienna Bone and Growth Center, Vienna, Austria.
| | - Agnès Linglart
- AP-HP, Paris Saclay University, INSERM, Reference Center for Rare Diseases of the Calcium and Phosphate Metabolism, Platform of Expertise for Rare Diseases, OSCAR Filière, EndoERN and BOND ERN Center, Endocrinology and Diabetes for Children, Bicêtre Paris Saclay Hospital, France
| | - Kim Bin
- Pediatric Orthopedic Surgery Angers University Hospital, Angers, France
| | - Frank Rauch
- Shriners Hospital for Children, Canada, Montreal, QC, Canada
| | - Stéphane Blouin
- Ludwig Boltzmann Institute of Osteology at Hanusch Hospital of OEGK and AUVA Trauma Centre Meidling, 1st Med. Department Hanusch Hospital, Vienna, Austria; Vienna Bone and Growth Center, Vienna, Austria
| | - Régis Coutant
- AP-HP, Paris Saclay University, INSERM, Reference Center for Rare Diseases of the Calcium and Phosphate Metabolism, Platform of Expertise for Rare Diseases, OSCAR Filière, EndoERN and BOND ERN Center, Endocrinology and Diabetes for Children, Bicêtre Paris Saclay Hospital, France; Department of Pediatric Endocrinology and Diabetology, Competence Center for Rare Diseases of the Calcium and Phosphate Metabolism, Angers University Hospital, Angers, France
| | - Aurélie Donzeau
- Department of Pediatric Endocrinology and Diabetology, Competence Center for Rare Diseases of the Calcium and Phosphate Metabolism, Angers University Hospital, Angers, France
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Calmarza P, Lapresta C, Martínez García M, Ochoa J, Sienes Bailo P, Acha Pérez J, Beltrán Audera J, González-Roca E. Musculoskeletal pain and muscular weakness as the main symptoms of adult hypophosphatasia in a Spanish cohort: clinical characterization and identification of a new ALPL gene variant. J Bone Miner Metab 2023; 41:654-665. [PMID: 37351650 DOI: 10.1007/s00774-023-01440-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Accepted: 05/15/2023] [Indexed: 06/24/2023]
Abstract
INTRODUCTION Hypophosphatasia (HPP) is a rare inherited disorder, caused by mutations in the alkaline phosphatase (ALPL) gene, which encodes for the tissue non-specific alkaline phosphatase (TNSALP) isoform of alkaline phosphatase (ALP). Adult HPP is one of the mild forms that presents with unspecific signs such as osteopenia, osteomalacia and muscle involvement. Our purpose was to identify and characterize possibly misdiagnosed adult HPP patients at a clinical and biochemical level. MATERIAL AND METHODS At the laboratory of Miguel Servet University Hospital we retrospectively reviewed serum ALP levels in adults over a 48-month period. The clinical records of individuals with consistently low ALP levels were reviewed to exclude secondary causes. Those with persistent hypophosphatasemia were screened for symptoms of HPP. The study participants were evaluated at biochemical and genetic levels. RESULTS We identified 705 ALP determinations (out of 384,000 processed) in 589 patients below the reference range (30 U/l). Only 21 patients with clinical signs and symptoms of HPP were selected for genetic testing. Finally, only 12 patients participated in the study, 83.3% of whom (10/12) harbored a pathogenic or likely pathogenic variant in a heterozygous state. The major symptoms of our cohort were the presence of musculoskeletal pain (100% of patients) and muscular weakness (83.3% patients). CONCLUSION Mild HPP patients presenting with diffuse symptoms such as musculoskeletal pain may be undiagnosed or misdiagnosed as osteoporosis patients by routine diagnosis. It is important to identify these individuals, to avoid inappropriate treatment with antiresorptive drugs.
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Affiliation(s)
- Pilar Calmarza
- Clinical Biochemistry Department, IIS Aragón, Miguel Servet University Hospital, Network Research Center in Cardiovascular Diseases (CIBERCV), University of Zaragoza, 50009, Zaragoza, Spain.
| | - Carlos Lapresta
- Preventive Medicine Department, Miguel Servet University Hospital, 50009, Zaragoza, Spain
| | | | - José Ochoa
- Occupational Risk Prevention Service, MAS Prevention, Zaragoza, Spain
| | - Paula Sienes Bailo
- Clinical Biochemistry Department, Miguel Servet University Hospital, 50009, Zaragoza, Spain
| | - Javier Acha Pérez
- Endocrinology Department, Miguel Servet University Hospital, 50009, Zaragoza, Spain
| | - Jesús Beltrán Audera
- Rheumatology department, Miguel Servet University Hospital, 50009, Zaragoza, Spain
| | - Eva González-Roca
- Molecular Biology Core Lab/Immunology Department, CDB. Hospital Clínic, Barcelona, Spain
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9
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Tachikawa K, Yamazaki M, Michigami T. A unique case of childhood hypophosphatasia caused by a novel heterozygous 51-bp in-frame deletion in the ALPL gene. Clin Pediatr Endocrinol 2023; 32:180-187. [PMID: 37362163 PMCID: PMC10288296 DOI: 10.1297/cpe.2023-0019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/13/2023] [Accepted: 04/18/2023] [Indexed: 06/28/2023] Open
Abstract
Hypophosphatasia (HPP) is caused by inactivating variants of the ALPL gene, which encodes tissue non-specific alkaline phosphatase (TNSALP). Among the six subtypes of HPP, childhood HPP presents after 6 months and before 18 yr of age, and is inherited in both autosomal dominant and autosomal recessive manners. Patients with childhood HPP have variable symptoms, including rickets-like bone changes, low bone mineral density (BMD), short stature, muscle weakness, craniosynostosis, and premature loss of deciduous teeth. Here, we describe a 7-yr-old boy with childhood HPP who showed short stature, impaired ossification of the carpal bones, and low BMD. Genetic testing identified a novel heterozygous 51-bp in-frame deletion in the ALPL gene (c.1482_1532del51), leading to the lack of 17 amino acids between Gly495 and Leu511 (p.Gly495_Leu511del). In vitro transfection experiments revealed the loss of enzymatic activity and the dominant-negative effect of the TNSALP[p.Gly495_Leu511del] variant; thus, the patient was diagnosed as having autosomal dominant HPP. The TNSALP[p.Gly495_Leu511del] variant was localized to the plasma membrane as was the wild-type TNSALP (TNSALP[WT]): however, co-immunoprecipitation experiments suggested a reduced dimerization between TNSALP[p.Gly495_Leu511del] and TNSALP[WT]. This case expands the variable clinical manifestation of childhood HPP and sheds light on the molecular bases underlying the dominant-negative effects of some TNSALP variants.
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Affiliation(s)
- Kanako Tachikawa
- Department of Bone and Mineral Research, Research Institute, Osaka Women's and Children's Hospital, Osaka Prefectural Hospital Organization, Osaka, Japan
| | - Miwa Yamazaki
- Department of Bone and Mineral Research, Research Institute, Osaka Women's and Children's Hospital, Osaka Prefectural Hospital Organization, Osaka, Japan
| | - Toshimi Michigami
- Department of Bone and Mineral Research, Research Institute, Osaka Women's and Children's Hospital, Osaka Prefectural Hospital Organization, Osaka, Japan
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10
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Riancho JA. Diagnostic Approach to Patients with Low Serum Alkaline Phosphatase. Calcif Tissue Int 2023; 112:289-296. [PMID: 36348061 DOI: 10.1007/s00223-022-01039-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Accepted: 10/26/2022] [Indexed: 11/09/2022]
Abstract
Increased serum levels of alkaline phosphatase (ALP) are widely recognized as a biochemical marker of many disorders affecting the liver or bone. However, the approach for patients with low ALP phosphatase is not well-established. Low serum ALP is an epiphenomenon of many severe acute injuries and diseases. Persistently low serum ALP may be secondary to drug therapy (including antiresorptives) or a variety of acquired disorders, such as malnutrition, vitamin and mineral deficiencies, endocrine disorders, etc. Hypophosphatasia, due to pathogenic variants of the ALPL gene, which encodes tissue non-specific ALP, is the most common genetic cause of low serum ALP. Marked bone hypomineralization is frequent in severe pediatric-onset cases. However, adult forms of hypophosphatasia usually present with milder manifestations, such as skeletal pain, chondrocalcinosis, calcific periarthritis, dental problems, and stress fractures. The diagnostic approach to these patients is discussed. Measuring several ALP substrates, such as pyrophosphate, pyridoxal phosphate, or phosphoethanolamine, may help to establish enzyme deficiency. Gene analysis showing a pathogenic variant in ALPL may confirm the diagnosis. However, a substantial proportion of patients show normal results after sequencing ALPL exons. It is still unknown if those patients carry unidentified mutations in regulatory regions of ALPL, epigenetic changes, or abnormalities in other genes.
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Affiliation(s)
- Jose A Riancho
- Departamento de Medicina y Psiquiatría, Universidad de Cantabria, Servicio de Medicina Interna, Hospital UM Valdecilla-IDIVAL, Av Valdecilla sn, 39008, Santander, Spain.
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11
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Kim I, Noh ES, Kim MS, Jang JH, Jeon TY, Choi HW, Cho SY. Six-year clinical outcomes of enzyme replacement therapy for perinatal lethal and infantile hypophosphatasia in Korea: Two case reports. Medicine (Baltimore) 2023; 102:e32800. [PMID: 36820543 PMCID: PMC9907957 DOI: 10.1097/md.0000000000032800] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/12/2023] Open
Abstract
INTRODUCTION Hypophosphatasia (HPP) is a genetic disease caused by loss-of-function mutations in ALPL, which encodes tissue-nonspecific alkaline phosphatase (ALP). Early diagnosis and treatment of perinatal and infantile HPP are important because of their high mortality rates. Enzyme replacement therapy (ERT) using human recombinant tissue-nonspecific ALP asfotase alfa was introduced in Korea in 2016. We report the first experience of ERT over 6 years for perinatal lethal and infantile HPP in Korea. PATIENT CONCERNS The first patient was a 6-week-old Korean boy with a failure to thrive. The second patient was an 8-day-old Korean-Uzbek body with generalized tonic-clonic seizure with cyanosis. DIAGNOSES HPP was suspected in both patients because of the very low level of ALP activity and rachitic findings on radiographs, and the disease was confirmed by Sanger sequencing of the ALPL gene. INTERVENTION The first patient with infantile HPP started ERT at 21 months of age and the second patient with perinatal HPP started ERT at 30 days of age. Both patients received asfotase alfa (2 mg/kg 3 times per week subcutaneously, adjusted to 3 mg/kg 3 times per week if required) for 6 years. OUTCOMES After 6 years of ERT, radiographic findings and growth standard deviation scores improved in both patients. The second patient showed no evidence of rickets after 3 years of ERT. Mechanical respiratory support and supplemental oxygen were not required after 4.5 years of treatment in the first patient and at 2 months after treatment in the second patient. CONCLUSION Among the 2 patients, the patient who started ERT early had a much better prognosis despite a more severe initial clinical presentation. Our results suggest that early diagnosis and prompt treatment play an important role in improving long-term prognosis and avoiding morbidity and premature mortality in patients with perinatal and infantile HPP.
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Affiliation(s)
- Insung Kim
- Department of Public Health Administration, Asan City Health Center, Asan, Korea
| | - Eu-Seon Noh
- Department of Pediatrics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Min-Sun Kim
- Department of Pediatrics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Ja-Hyun Jang
- Department of Laboratory Medicine and Genetics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Tae Yeon Jeon
- Department of Radiology and Center for Imaging Science, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Hae Won Choi
- Department of Orthodontics, The Institute of Oral Health Science, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Sung Yoon Cho
- Department of Pediatrics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
- * Correspondence: Sung Yoon Cho, Department of Pediatrics, Samsung Medical Center, Sungkyunkwan University School of Medicine, 81 Irwon-ro, Gangnam-gu, Seoul 06351, Korea (e-mail: )
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12
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Suzue M, Suga K, Teketani T, Nakagawa R, Urushihara M. Chylous ascites complicating perinatal severe hypophosphatasia in an infant on high-setting ventilation and enzyme replacement therapy. Pediatr Int 2023; 65:e15585. [PMID: 37475513 DOI: 10.1111/ped.15585] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Revised: 05/16/2023] [Accepted: 05/31/2023] [Indexed: 07/22/2023]
Affiliation(s)
- Masashi Suzue
- Department of Pediatrics, Tokushima University Hospital, Tokushima, Japan
| | - Kenichi Suga
- Department of Pediatrics, Tokushima University Hospital, Tokushima, Japan
| | - Takeshi Teketani
- Department of Pediatrics, Shimane University Faculty of Medicine, Izumo, Japan
| | - Ryuji Nakagawa
- Department of Pediatrics, Tokushima University Hospital, Tokushima, Japan
| | - Maki Urushihara
- Department of Pediatrics, Tokushima University Hospital, Tokushima, Japan
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13
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Childhood Hypophosphatasia Associated with a Novel Biallelic ALPL Variant at the TNSALP Dimer Interface. Int J Mol Sci 2022; 24:ijms24010282. [PMID: 36613725 PMCID: PMC9820760 DOI: 10.3390/ijms24010282] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2022] [Revised: 12/08/2022] [Accepted: 12/15/2022] [Indexed: 12/28/2022] Open
Abstract
The goal of this study was to perform a clinical and molecular investigation in an eight-year-old female child diagnosed with hypophosphatasia (HPP). The proband and her family were evaluated by medical and dental histories, biochemical analyses, radiographic imaging, and genetic analysis of the tissue-nonspecific alkaline phosphatase (ALPL) gene. A bioinformatic analysis was performed to predict the structural and functional impact of the point mutations in the tissue-nonspecific alkaline phosphatase (TNSALP) molecule and to define their potential contribution to the phenotype. We identified a novel combination of heterozygous ALPL missense variants in the proband, p.Ala33Val and p.Asn47His, compatible with an autosomal recessive mode of inheritance and resulting in skeletal and dental phenotypes. Computational modeling showed that the affected Asn47 residue is located in the coil structure close to the N-terminal α-helix, whereas the affected Ala33 residue is localized in the N-terminal α-helix. Both affected residues are located close to the homodimer interface, suggesting they may impair TNSALP dimer formation and stability. Clinical and biochemical follow-up revealed improvements after six years of ERT. Reporting this novel combination of ALPL variants in childhood HPP provides new insights into genotype-phenotype associations for HPP and specific sites within the TNSALP molecule potentially related to a childhood-onset HPP and skeletal and dental manifestations. Beneficial effects of ERT are implicated in skeletal and dental tissues.
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14
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Beck NM, Sagaser KG, Lawson CS, Hertenstein C, Jachens A, Forster KR, Miller KA, Jelin AC, Blakemore KJ, Hoover‐Fong J. Not just a carrier: Clinical presentation and management of patients with heterozygous disease-causing alkaline phosphatase (ALPL) variants identified through expanded carrier screening. Mol Genet Genomic Med 2022; 11:e2056. [PMID: 36444396 PMCID: PMC9834184 DOI: 10.1002/mgg3.2056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2022] [Revised: 07/05/2022] [Accepted: 09/01/2022] [Indexed: 12/02/2022] Open
Abstract
Hypophosphatasia (HPP) is an underrecognized, complex bone mineralization disorder with variable manifestations caused by one or two deleterious variants in the alkaline phosphatase (ALPL) gene. Expanded carrier screening (ECS), inclusive of ALPL, intends to inform reproductive risk but may incidentally reveal an HPP diagnosis with 50% familial risks. We sought to investigate at-risk individuals and develop a multidisciplinary referral and evaluation protocol for ECS-identified ALPL heterozygosity. A retrospective database query of ECS results from 8 years to 1 month for heterozygous pathogenic/likely pathogenic ALPL variants was completed. We implemented a clinical protocol for diagnostic testing and imaging, counseling, and interdisciplinary care management for identified patients, and outcomes were documented. Heterozygous ALPL variants were identified in 12/2248 unrelated patients undergoing ECS (0.53%; heterozygote frequency 1/187). Of 10 individuals successfully contacted, all demonstrated symptomatology and/or alkaline phosphatase values consistent with HPP. ECS may reveal incidental health risks, including recognition of missed HPP diagnoses in ALPL heterozygotes. In our cohort, all ECS-identified ALPL heterozygotes with clinical and/or biochemical data available demonstrated features of HPP. Referral to a genetics professional familiar with HPP is indicated for family history assessment, genetic counseling, cascade testing, and long-term bone health management.
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Affiliation(s)
- Natalie M. Beck
- Greenberg Center for Skeletal Dysplasias, Department Genetic of MedicineJohns Hopkins University School of MedicineBaltimoreMarylandUSA,Genome Medical ServicesSan FranciscoCaliforniaUSA
| | - Katelynn G. Sagaser
- Division of Maternal Fetal Medicine, Department of Gynecology and ObstetricsJohns Hopkins University School of MedicineBaltimoreMarylandUSA,JunoDxSan DiegoCaliforniaUSA
| | - Cathleen S. Lawson
- Division of Maternal Fetal Medicine, Department of Gynecology and ObstetricsJohns Hopkins University School of MedicineBaltimoreMarylandUSA
| | - Christine Hertenstein
- Division of Maternal Fetal Medicine, Department of Gynecology and ObstetricsJohns Hopkins University School of MedicineBaltimoreMarylandUSA
| | - Ashley Jachens
- Center for Maternal and Fetal MedicineHoward County General Hospital, Johns Hopkins HospitalBaltimoreMarylandUSA
| | - Katherine R. Forster
- Center for Fetal TherapyJohns Hopkins University School of MedicineBaltimoreMarylandUSA,Sibley Memorial Hospital Maternal Fetal MedicineWashingtonDistrict of ColumbiaUSA
| | - Kristen A. Miller
- Division of Maternal Fetal Medicine, Department of Gynecology and ObstetricsJohns Hopkins University School of MedicineBaltimoreMarylandUSA
| | - Angie C. Jelin
- Division of Maternal Fetal Medicine, Department of Gynecology and ObstetricsJohns Hopkins University School of MedicineBaltimoreMarylandUSA
| | - Karin J. Blakemore
- Division of Maternal Fetal Medicine, Department of Gynecology and ObstetricsJohns Hopkins University School of MedicineBaltimoreMarylandUSA
| | - Julie Hoover‐Fong
- Greenberg Center for Skeletal Dysplasias, Department Genetic of MedicineJohns Hopkins University School of MedicineBaltimoreMarylandUSA
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15
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Koleske ML, McInnes G, Brown JEH, Thomas N, Hutchinson K, Chin MY, Koehl A, Arkin MR, Schlessinger A, Gallagher RC, Song YS, Altman RB, Giacomini KM. Functional genomics of OCTN2 variants informs protein-specific variant effect predictor for Carnitine Transporter Deficiency. Proc Natl Acad Sci U S A 2022; 119:e2210247119. [PMID: 36343260 PMCID: PMC9674959 DOI: 10.1073/pnas.2210247119] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2022] [Accepted: 09/16/2022] [Indexed: 11/09/2022] Open
Abstract
Genetic variants in SLC22A5, encoding the membrane carnitine transporter OCTN2, cause the rare metabolic disorder Carnitine Transporter Deficiency (CTD). CTD is potentially lethal but actionable if detected early, with confirmatory diagnosis involving sequencing of SLC22A5. Interpretation of missense variants of uncertain significance (VUSs) is a major challenge. In this study, we sought to characterize the largest set to date (n = 150) of OCTN2 variants identified in diverse ancestral populations, with the goals of furthering our understanding of the mechanisms leading to OCTN2 loss-of-function (LOF) and creating a protein-specific variant effect prediction model for OCTN2 function. Uptake assays with 14C-carnitine revealed that 105 variants (70%) significantly reduced transport of carnitine compared to wild-type OCTN2, and 37 variants (25%) severely reduced function to less than 20%. All ancestral populations harbored LOF variants; 62% of green fluorescent protein (GFP)-tagged variants impaired OCTN2 localization to the plasma membrane of human embryonic kidney (HEK293T) cells, and subcellular localization significantly associated with function, revealing a major LOF mechanism of interest for CTD. With these data, we trained a model to classify variants as functional (>20% function) or LOF (<20% function). Our model outperformed existing state-of-the-art methods as evaluated by multiple performance metrics, with mean area under the receiver operating characteristic curve (AUROC) of 0.895 ± 0.025. In summary, in this study we generated a rich dataset of OCTN2 variant function and localization, revealed important disease-causing mechanisms, and improved upon machine learning-based prediction of OCTN2 variant function to aid in variant interpretation in the diagnosis and treatment of CTD.
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Affiliation(s)
- Megan L. Koleske
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, CA 94143
| | - Gregory McInnes
- Biomedical Informatics Training Program, Stanford University, Stanford, CA 94305
- Empirico Inc., San Diego, CA 92122
| | - Julia E. H. Brown
- Program in Bioethics, University of California, San Francisco, CA 94143
- Institute for Health & Aging, University of California, San Francisco, CA 94143
| | - Neil Thomas
- Computer Science Division, University of California, Berkeley, CA 94720
| | - Keino Hutchinson
- Department of Pharmacological Sciences, Icahn School of Medicine at Mt. Sinai, New York, NY 10029
| | - Marcus Y. Chin
- Small Molecule Discovery Center, Department of Pharmaceutical Chemistry, University of California, San Francisco, CA 94143
| | - Antoine Koehl
- Department of Statistics, University of California, Berkeley, CA 94720
| | - Michelle R. Arkin
- Small Molecule Discovery Center, Department of Pharmaceutical Chemistry, University of California, San Francisco, CA 94143
| | - Avner Schlessinger
- Department of Pharmacological Sciences, Icahn School of Medicine at Mt. Sinai, New York, NY 10029
| | - Renata C. Gallagher
- Institute for Human Genetics, University of California, San Francisco, CA 94143
- Department of Pediatrics, University of California, San Francisco, CA 94143
| | - Yun S. Song
- Computer Science Division, University of California, Berkeley, CA 94720
- Department of Statistics, University of California, Berkeley, CA 94720
| | - Russ B. Altman
- Department of Bioengineering, Stanford University, Stanford, CA 94305
- Department of Genetics, Stanford University, Stanford, CA 94305
| | - Kathleen M. Giacomini
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, CA 94143
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16
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Glotov OS, Savostyanov KV, Nagornova TS, Chernov AN, Fedyakov MA, Raspopova AN, Krasnoukhov KN, Danilov LG, Moiseeva NV, Kalinin RS, Tsai VV, Eismont YA, Voinova VY, Vitebskaya AV, Gurkina EY, Kuzenkova LM, Sosnina IB, Pushkov AA, Zhanin IS, Zakharova EY. Clinical and Genetic Characteristics of Pediatric Patients with Hypophosphatasia in the Russian Population. Int J Mol Sci 2022; 23:ijms232112976. [PMID: 36361766 PMCID: PMC9654387 DOI: 10.3390/ijms232112976] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2022] [Revised: 10/14/2022] [Accepted: 10/17/2022] [Indexed: 11/16/2022] Open
Abstract
(1) Hypophosphatasia (HPP) is a rare inherited disease caused by mutations (pathogenic variants) in the ALPL gene which encodes tissue-nonspecific alkaline phosphatase (TNSALP). HPP is characterized by impaired bone mineral metabolism due to the low enzymatic activity of TNSALP. Knowledge about the structure of the gene and the features and functions of various ALPL gene variants, taking into account population specificity, gives an understanding of the hereditary nature of the disease, and contributes to the diagnosis, prevention, and treatment of the disease. The purpose of the study was to describe the spectrum and analyze the functional features of the ALPL gene variants, considering various HPP subtypes and clinical symptoms in Russian children. (2) From 2014−2021, the study included the blood samples obtained from 1612 patients with reduced alkaline phosphatase activity. The patients underwent an examination with an assessment of their clinical symptoms and biochemical levels of TNSALP. DNA was isolated from dried blood spots (DBSs) or blood from the patients to search for mutations in the exons of the ALPL gene using Sanger sequencing. The PCR products were sequenced using a reagent BigDye Terminator 3.1 kit (Applied Biosystems). Statistical analysis was performed using the GraphPad Prism 8.01 software. (3) The most common clinical symptoms in Russian patients with HPP and two of its variants (n = 22) were bone disorders (75%), hypomyotonia (50%), and respiratory failure (50%). The heterozygous carriage of the causal variants of the ALPL gene was detected in 225 patients. A total of 2 variants were found in 27 patients. In this group (n = 27), we identified 28 unique variants of the ALPL gene, of which 75.0% were missense, 17.9% were frameshift, 3.6% were splicing variants, and 3.6% were duplications. A total of 39.3% (11/28) of the variants were pathogenic, with two variants being probably pathogenic, and 15 variants had unknown clinical significance (VUS). Among the VUS group, 28.6% of the variants (7/28) were discovered by us for the first time. The most common variants were c.571G > A (p.Glu191Lys) and c.1171del (Arg391Valfs*12), with frequencies of 48.2% (13/28) and 11% (3/28), respectively. It was found that the frequency of nonsense variants of the ALPL gene was higher (p < 0.0001) in patients with the perinatal form compared to the infantile and childhood forms of HPP. Additionally, the number of homozygotes in patients with the perinatal form exceeded (p < 0.01) the frequencies of these genotypes in children with infantile and childhood forms of HPP. On the contrary, the frequencies of the compound-heterozygous and heterozygous genotypes were higher (p < 0.01) in patients with infantile childhood HPP than in perinatal HPP. In the perinatal form, residual TNSALP activity was lower (p < 0.0005) in comparison to the infantile and childhood (p < 0.05) forms of HPP. At the same time, patients with the heterozygous and compound-heterozygous genotypes (mainly missense variants) of the ALPL gene had greater residual activity (of the TNSALP protein) regarding those homozygous patients who were carriers of the nonsense variants (deletions and duplications) of the ALPL gene. Residual TNSALP activity was lower (p < 0.0001) in patients with pathogenic variants encoding the amino acids from the active site and the calcium and crown domains in comparison with the nonspecific region of the protein.
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Affiliation(s)
- Oleg S. Glotov
- Department of Genomic Medicine, D. O. Ott Research Institute of Obstetrics, Gynaecology and Reproductology, 199034 Saint-Petersburg, Russia
- Department of Experimental Medical Virology, Molecular Genetics and Biobanking of Pediatric Research and Clinical Center for Infectious Diseases, 197022 Saint-Petersburg, Russia
- Correspondence: (O.S.G.); (A.N.C.)
| | | | | | - Alexandr N. Chernov
- Department of Genomic Medicine, D. O. Ott Research Institute of Obstetrics, Gynaecology and Reproductology, 199034 Saint-Petersburg, Russia
- Bioenergetics Department of Life Sciences, The National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel
- Department of General Pathology and Pathological Physiology, Institute of Experimental Medicine, 197376 Saint-Petersburg, Russia
- Correspondence: (O.S.G.); (A.N.C.)
| | - Mikhail A. Fedyakov
- CerbaLab Ltd., 199106 Saint-Petersburg, Russia
- City Hospital No. 40, St.-Petersburg, 9 Borisova Str., Sestrorezk, 197706 Saint-Petersburg, Russia
| | | | | | - Lavrentii G. Danilov
- CerbaLab Ltd., 199106 Saint-Petersburg, Russia
- Department of Genetics and Biotechnology, Saint-Petersburg State University, 199034 Saint-Petersburg, Russia
| | | | - Roman S. Kalinin
- Department of Genomic Medicine, D. O. Ott Research Institute of Obstetrics, Gynaecology and Reproductology, 199034 Saint-Petersburg, Russia
- Department of Experimental Medical Virology, Molecular Genetics and Biobanking of Pediatric Research and Clinical Center for Infectious Diseases, 197022 Saint-Petersburg, Russia
| | - Victoria V. Tsai
- Department of Genomic Medicine, D. O. Ott Research Institute of Obstetrics, Gynaecology and Reproductology, 199034 Saint-Petersburg, Russia
- Department of Experimental Medical Virology, Molecular Genetics and Biobanking of Pediatric Research and Clinical Center for Infectious Diseases, 197022 Saint-Petersburg, Russia
- CerbaLab Ltd., 199106 Saint-Petersburg, Russia
| | - Yuri A. Eismont
- Department of Experimental Medical Virology, Molecular Genetics and Biobanking of Pediatric Research and Clinical Center for Infectious Diseases, 197022 Saint-Petersburg, Russia
- CerbaLab Ltd., 199106 Saint-Petersburg, Russia
| | - Victoria Y. Voinova
- Veltischev Research and Clinical Institute for Pediatrics, Pirogov Russian National Research Medical University, 117997 Moscow, Russia
| | - Alisa V. Vitebskaya
- Department of Children’s Diseases of N.F. Filatov Clinical Institute for Children’s Health, I.M. Sechenov First Moscow State Medical University, 119991 Moscow, Russia
| | - Elena Y. Gurkina
- Children’s Rehabilitation Clinic Almazov National Medical Research Centre, 197341 Saint-Petersburg, Russia
| | - Ludmila M. Kuzenkova
- National Medical Research Center of Children Health, 119991 Moscow, Russia
- Department of Children’s Diseases of N.F. Filatov Clinical Institute for Children’s Health, I.M. Sechenov First Moscow State Medical University, 119991 Moscow, Russia
| | - Irina B. Sosnina
- Saint-Petersburg State Budgetary Healthcare Institution “Consulting and Diagnostic Center for Children”, 192289 Saint-Petersburg, Russia
| | | | - Ilya S. Zhanin
- National Medical Research Center of Children Health, 119991 Moscow, Russia
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Shajani-Yi Z, Ayala-Lopez N, Black M, Dahir KM. Urine phosphoethanolamine is a specific biomarker for hypophosphatasia in adults. Bone 2022; 163:116504. [PMID: 35878747 DOI: 10.1016/j.bone.2022.116504] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/26/2022] [Revised: 07/04/2022] [Accepted: 07/19/2022] [Indexed: 11/02/2022]
Abstract
OBJECTIVES We investigated the utility of urine phosphoethanolamine (PEA) as a marker to aid in diagnosing and/or confirming hypophosphatasia (HPP) in adults and for monitoring patients on enzyme replacement therapy (ERT). METHODS Data was collected from seventy-eight adults who were referred to the Vanderbilt Program for Metabolic Bone Disease for evaluation of a possible or confirmatory HPP diagnosis between July 2014 through December 2019. Fifty-nine patients were diagnosed with HPP and nineteen were excluded from a diagnosis of HPP. The urine PEA results of those patients with a confirmed diagnosis of HPP and those patients with a diagnosis of HPP excluded were captured and compared to other laboratory and clinical parameters consistent with HPP, including alkaline phosphatase (ALP) activity, plasma pyridoxal 5'-phosphate (PLP), the presence of musculoskeletal abnormalities, and genetic testing for pathogenic mutations in ALPL. RESULTS Initial urine PEA values in patients in our HPP cohort and not on ERT were significantly higher (median = 150.0 nmol/mg creatinine, IQR = 82.0-202.0) compared patients in our HPP negative group (median 18.0 nmol/mg creatinine, IQR = 14.0-30.0, p < 0.0001) and higher than patients on ERT (median 65.0 nmol/mg creatinine, IQR = 45.3-79.8). Patients who began ERT had a decline in urine PEA levels after treatment with a mean decrease of 68.1 %. Plasma ALP levels were significantly lower in the group of patients with HPP and not on ERT group (median = 24.0 U/L, IQR = 15.0-29.50) compared to the patients without HPP (median = 45.50 U/L, IQR = 34.0-62.0;) and plasma PLP levels were significantly higher in the HPP non-ERT group (median = 284.0 nmol/L, IQR = 141.0-469.4) compared to the patients without HPP (median = 97.5 nmol/L, IQR = 43.7-206.0;). The area under the curve (AUC) of urine PEA, ALP, and PLP to distinguish between HPP and non-HPP patients is 0.968, 0.927 and 0.781, respectively, in our cohort. Urine PEA had 100 % specificity (95 % CI of 83.2 % to 100.0 %) for diagnosing HPP at a value >53.50 nmol/mg creatinine with a sensitivity of 88.4 %; 95%CI 75.5 to 94.9 %. ALP had a 100 % specificity (95 % CI of 82.4 % to 100.0 %) for diagnosing HPP at a value <30.5 U/L with a sensitivity of 77.2 %; (95%CI 64.8 to 86.2 %). PLP had a 100 % specificity (95 % CI of 81.6 % to 100.0 %) for diagnosing HPP at a value >436 nmol/L with a sensitivity of 26.9 %; (95%CI 16.8 to 40.3 %). The most common pathogenic or likely pathogenic mutations in our cohort were c.1250A>G (p.Asn417Ser), c.1133A>T (p.Asp378Val), c.881A>C (p.Asp294Ala), c.1171C>T (p.Arg391Cys), and c.571G>A, (p.Glu191Lys). CONCLUSIONS Urine PEA is a promising diagnostic and confirmatory marker for HPP in patients undergoing investigation for HPP. Urine PEA also has potential use as a marker to monitor ERT compliance. Future studies are necessary to evaluate the association between PEA levels and clinical outcomes.
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Affiliation(s)
- Zahra Shajani-Yi
- Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, TN, USA; Department of Pathology, Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Nadia Ayala-Lopez
- Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Margo Black
- Division of Endocrinology, Program for Metabolic Bone Disorders, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Kathryn McCrystal Dahir
- Division of Endocrinology, Program for Metabolic Bone Disorders, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA.
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18
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Hepp N, Folkestad L, Møllebæk S, Frederiksen AL, Duno M, Jørgensen NR, Hermann AP, Jensen JEB. Bone-microarchitecture and bone-strength in a sample of adults with hypophosphatasia and a matched reference population assessed by HR-pQCT and impact microindentation. Bone 2022; 160:116420. [PMID: 35421614 DOI: 10.1016/j.bone.2022.116420] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/07/2022] [Revised: 04/03/2022] [Accepted: 04/07/2022] [Indexed: 12/23/2022]
Abstract
BACKGROUND Hypophosphatasia (HPP) is an autosomal recessive or dominate disease affecting bone mineralization, and adults with HPP are in risk to develop metatarsal stress fractures and femoral pseudofractures. Given to the scarce data on the bone quality and its association to the fracture risk in adults with HPP, this study aimed to evaluate bone turnover, bone strength and structure in adults with HPP. METHODS In this cross-sectional study, we included 14 adults with genetically verified HPP and 14 sex-, age-, BMI-, and menopausal status-matched reference individuals. We analyzed bone turnover markers, and measured bone material strength index (BMSi) by impact microindentation. Bone geometry, volumetric density and bone microarchitecture as well as failure load at the distal radius and tibia were evaluated using a second-generation high-resolution peripheral quantitative computed tomography system. RESULTS Bone turnover markers did not differ between patients with HPP and reference individuals. BMSi did not differ between the groups (67.90 [63.75-76.00] vs 65.45 [58.43-69.55], p = 0.149). Parameters of bone geometry and volumetric density did not differ between adults with HPP and the reference group. Patients with HPP had a tendency toward higher trabecular separation (0.664 [0.613-0.724] mm vs 0.620 [0.578-0.659] mm, p = 0.054) and inhomogeneity of trabecular network (0.253 [0.235-0.283] mm vs 0.229 [0.208-0.252] mm, p = 0.056) as well as lower trabecular bone volume fraction (18.8 [16.4-22.7] % vs 22.8 [20.6-24.7] %, p = 0.054) at the distal radius. In addition, compound heterozygous adults with HPP had a significantly higher cortical porosity at the distal radius than reference individuals (1.5 [0.9-2.2] % vs 0.7 [0.6-0.7] %, p = 0.041). CONCLUSIONS BMSi is not reduced in adults with HPP. Increased cortical porosity may contribute to the occurrence of femoral pseudofractures in compound heterozygous adults with HPP. However, further studies investigating larger cohorts of adults with HPP using methods of bone histomorphometry are recommended to adequately assess the bone quality in adults with HPP.
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Affiliation(s)
- Nicola Hepp
- Dept. of Endocrinology, Copenhagen University Hospital Hvidovre, Kettegaard Alle 30, 2650 Hvidovre, Denmark; Dept. of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3 B, 2200 Copenhagen, Denmark.
| | - Lars Folkestad
- Dept. of Endocrinology and Metabolism, Odense University Hospital, Kløvervænget 6, 5000 Odense C, Denmark; Dept. of Clinical Research, University of Southern Denmark, Winsløwparken 19, 5000 Odense C, Denmark
| | - Simone Møllebæk
- Dept. of Endocrinology and Metabolism, Odense University Hospital, Kløvervænget 6, 5000 Odense C, Denmark
| | - Anja Lisbeth Frederiksen
- Dept. of Clinical Genetics, Aalborg University Hospital, Ladegaardsgade 5, 9000 Aalborg C, Denmark; Dept. of Clinical Research, Aalborg University, Fredrik Bajers Vej 7K, 9220 Aalborg Ø, Denmark
| | - Morten Duno
- Dept. of Clinical Genetics, University Hospital Copenhagen Rigshospitalet, Blegdamsvej 9, 2100 Copenhagen, Denmark
| | - Niklas Rye Jørgensen
- Dept. of Clinical Biochemistry, Rigshospitalet, Valdemar Hansens Vej 13, 2600 Glostrup, Denmark; Dept. of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3 B, 2200 Copenhagen, Denmark
| | - Anne Pernille Hermann
- Dept. of Endocrinology and Metabolism, Odense University Hospital, Kløvervænget 6, 5000 Odense C, Denmark
| | - Jens-Erik Beck Jensen
- Dept. of Endocrinology, Copenhagen University Hospital Hvidovre, Kettegaard Alle 30, 2650 Hvidovre, Denmark; Dept. of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3 B, 2200 Copenhagen, Denmark
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19
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Marini F, Masi L, Giusti F, Cianferotti L, Cioppi F, Marcucci G, Ciuffi S, Biver E, Toro G, Iolascon G, Iantomasi T, Brandi ML. ALPL Genotypes in Patients With Atypical Femur Fractures or Other Biochemical and Clinical Signs of Hypophosphatasia. J Clin Endocrinol Metab 2022; 107:e2087-e2094. [PMID: 34935951 DOI: 10.1210/clinem/dgab914] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Indexed: 11/19/2022]
Abstract
CONTEXT Hypophosphatasia (HPP) is a rare metabolic disorder caused by deficiency of alkaline phosphatase (ALP) enzyme activity, leading to defective mineralization, due to pathogenic variants of the ALPL gene, encoding the tissue nonspecific alkaline phosphatase (TNSALP) enzyme. Inheritance can be autosomal recessive or autosomal dominant. An abnormal ALPL genetic test enables accurate diagnosis, avoiding the administration of contraindicated antiresorptive drugs that, in patients with HPP, substantially increase the risk of atypical femur fractures (AFFs) and worsen the fracture healing process that is usually already compromised in these patients. OBJECTIVE Performing ALPL genetic testing to identify rare variants in suspected adult patients with HPP. Comparing frequencies of ALPL common variants in individuals with biochemical and/or clinical signs suggestive of adult HPP and non-HPP controls, and among different clinical subgroups of patients with a clinical suspicion of adult HPP. METHODS Patients with suspected adult HPP were retrospectively selected for the genetic testing of the ALPL gene. Patients included were from 3 main European Bone Units (Florence, Naples, and Geneva); 106 patients with biochemical and/or clinical signs suggestive of a mild form of HPP were included. RESULTS Genetic testing led to the identification of a heterozygote rare variant in 2.8% of cases who were initially referred as suspected osteoporosis. The analysis of frequencies of ALPL common variants showed a high prevalence (30.8%) of homozygosity in subjects who developed an AFF, in association with normal serum total ALP activity. CONCLUSION The results suggest homozygosity of common ALPL variants as a possible genetic mark of risk for these fractures.
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Affiliation(s)
- Francesca Marini
- Department of Experimental and Clinical Biomedical Sciences, University of Florence, Florence, Italy
- F.I.R.M.O. Italian Foundation for the Research on Bone Diseases, Florence, Italy
| | - Laura Masi
- University Hospital of Florence, Azienda Ospedaliero-Universitaria Careggi (AOUC), Florence, Italy
| | - Francesca Giusti
- Department of Experimental and Clinical Biomedical Sciences, University of Florence, Florence, Italy
| | - Luisella Cianferotti
- Department of Experimental and Clinical Biomedical Sciences, University of Florence, Florence, Italy
- University Hospital of Florence, Azienda Ospedaliero-Universitaria Careggi (AOUC), Florence, Italy
| | - Federica Cioppi
- University Hospital of Florence, Azienda Ospedaliero-Universitaria Careggi (AOUC), Florence, Italy
| | - Gemma Marcucci
- Department of Experimental and Clinical Biomedical Sciences, University of Florence, Florence, Italy
- University Hospital of Florence, Azienda Ospedaliero-Universitaria Careggi (AOUC), Florence, Italy
| | - Simone Ciuffi
- Department of Experimental and Clinical Biomedical Sciences, University of Florence, Florence, Italy
| | - Emmanuel Biver
- Division of Bone Diseases, Geneva University Hospitals and Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Giuseppe Toro
- Department of Medical and Surgical Specialties and Dentistry, University of Campania "Luigi Vanvitelli", Naples, Italy
| | - Giovanni Iolascon
- Department of Medical and Surgical Specialties and Dentistry, University of Campania "Luigi Vanvitelli", Naples, Italy
| | - Teresa Iantomasi
- Department of Experimental and Clinical Biomedical Sciences, University of Florence, Florence, Italy
| | - Maria Luisa Brandi
- F.I.R.M.O. Italian Foundation for the Research on Bone Diseases, Florence, Italy
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20
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Thrailkill KM, Kalaitzoglou E, Fowlkes JL. Emerging therapies for the treatment of rare pediatric bone disorders. Front Pediatr 2022; 10:1012816. [PMID: 36304528 PMCID: PMC9592743 DOI: 10.3389/fped.2022.1012816] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/05/2022] [Accepted: 09/09/2022] [Indexed: 11/24/2022] Open
Abstract
In recent years, new therapies for the treatment of rare pediatric bone disorders have emerged, guided by an increasing understanding of the genetic and molecular etiology of these diseases. Herein, we review three such disorders, impacted by debilitating deficits in bone mineralization or cartilage ossification, as well as the novel disease-modifying drugs that are now available to treat these conditions. Specifically, we discuss asfotase alfa, burosumab-twza, and vosoritide, for the treatment of hypophosphatasia, X-linked hypophosphatemia and achondroplasia, respectively. For each skeletal disorder, an overview of the clinical phenotype and natural history of disease is provided, along with a discussion of the clinical pharmacology, mechanism of action and FDA indication for the relevant medication. In each case, a brief review of clinical trial data supporting drug development for each medication is provided. Additionally, guidance as to drug dosing and long-term monitoring of adverse events and pediatric efficacy is presented, to aid the clinician seeking to utilize these novel therapies in their practice, or to become familiar with the healthcare expectations for children receiving these medications through specialized multidisciplinary clinics. The availability of these targeted therapies now significantly augments treatment options for conditions in which past therapy has relied upon less specific, symptomatic medical and orthopedic care.
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Affiliation(s)
- Kathryn M Thrailkill
- Department of Pediatrics, University of Kentucky Barnstable Brown Diabetes Center, University of Kentucky College of Medicine, Lexington, KY, United States
| | - Evangelia Kalaitzoglou
- Department of Pediatrics, University of Kentucky Barnstable Brown Diabetes Center, University of Kentucky College of Medicine, Lexington, KY, United States
| | - John L Fowlkes
- Department of Pediatrics, University of Kentucky Barnstable Brown Diabetes Center, University of Kentucky College of Medicine, Lexington, KY, United States
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21
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Zhang Q, Qin Z, Yi S, Wei H, Zhou XZ, Shen F. Case Report: Variations in the ALPL Gene in Chinese Patients With Hypophosphatasia. Front Genet 2021; 12:732621. [PMID: 34712267 PMCID: PMC8546181 DOI: 10.3389/fgene.2021.732621] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Accepted: 09/27/2021] [Indexed: 01/27/2023] Open
Abstract
Background: Hypophosphatasia (HPP) is an autosomal genetic disorder characterized biochemically by abnormal of bone parameters and serum alkaline phosphatase (ALP) activity as well as clinically by deficiency of teeth and bone mineralization. The clinical presentation is a continuum ranging from a prenatal lethal form with no skeletal mineralization to a mild form with late adult onset presenting with non-pathognomonic symptoms. ALP deficiency is the key to the pathogenesis of abnormal metabolism and skeletal system damage in HPP patients. Methods: We investigated five patients with skeletal dysplasia in the clinic. Whole-exome sequencing was performed in order to aid diagnosis of the patients. Results: Eight variants in the ALPL gene in the five unrelated Chinese patients (PA-1: c.649_650insC and c.707A > G; PA2: c.98C > T and c.707A > G; PA3: c.407G > A and c.650delTinsCTAA; PA4: c.1247G > T (homozygous); PA5: c.406C > T and c.1178A > G; NM_000478.5) were found. These variations caused two types of HPP: perinatal HPP and Odonto HPP. All cases reported in this study were autosomal recessive. Among the variants, c.1247G > T/p.Gly416Val (PA-4); c.1178A > G/p.Asn393Ser (PA-5) and c.707A > G/p.Tyr236Cys (PA-1, PA-2) have never been reported before. Conclusion: Clinical phenotypes of perinatal HPP (PA-1,PA-2,PA-3 and PA-4) include skeletal dysplasia, shorter long bones, bowing of long bones, tetraphocomelia, abnormal posturing and abnormal bone ossification. Odonto HPP (PA-5) only presents as dental abnormality with severe dental caries and decreased ALP activity. Our study extends the pool of ALPL variants in different populations.
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Affiliation(s)
- Qiang Zhang
- The Maternal and Child Health Care Hospital of Guangxi Zhuang Autonomous Region, Guangxi Birth Defects Prevention and Control Institute, Nanning, China.,Laboratory of Genetic Metabolism Center, Maternal and Child Health Hospital of Guangxi Zhuang Autonomous Region, Nanning, China
| | - Zailong Qin
- The Maternal and Child Health Care Hospital of Guangxi Zhuang Autonomous Region, Guangxi Birth Defects Prevention and Control Institute, Nanning, China.,Laboratory of Genetic Metabolism Center, Maternal and Child Health Hospital of Guangxi Zhuang Autonomous Region, Nanning, China
| | - Shang Yi
- Laboratory of Genetic Metabolism Center, Maternal and Child Health Hospital of Guangxi Zhuang Autonomous Region, Nanning, China
| | - Hao Wei
- Laboratory of Genetic Metabolism Center, Maternal and Child Health Hospital of Guangxi Zhuang Autonomous Region, Nanning, China
| | - Xun Zhao Zhou
- Laboratory of Genetic Metabolism Center, Maternal and Child Health Hospital of Guangxi Zhuang Autonomous Region, Nanning, China
| | - Fei Shen
- Laboratory of Genetic Metabolism Center, Maternal and Child Health Hospital of Guangxi Zhuang Autonomous Region, Nanning, China
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22
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Hepp N, Frederiksen AL, Duno M, Præst Holm J, Rye Jørgensen N, Beck Jensen JE. Biochemical, clinical and genetic characteristics in adults with persistent hypophosphatasaemia; Data from an endocrinological outpatient clinic in Denmark. Bone Rep 2021; 15:101101. [PMID: 34258332 PMCID: PMC8256181 DOI: 10.1016/j.bonr.2021.101101] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Revised: 06/18/2021] [Accepted: 06/23/2021] [Indexed: 12/18/2022] Open
Abstract
Background Hypophosphatasia (HPP) is an inborn disease caused by pathogenic variants in ALPL. Low levels of alkaline phosphatase (ALP) are a biochemical hallmark of the disease. Scarce knowledge about the prevalence of HPP in Scandinavia exists, and the variable clinical presentations make diagnostics challenging. The aim of this study was to investigate the prevalence of ALPL variants as well as the clinical and biochemical features among adults with endocrinological diagnoses and persistent hypophosphatasaemia. Methods A biochemical database containing ALP measurements of 26,121 individuals was reviewed to identify adults above 18 years of age with persistently low levels of ALP beneath range (≤ 35 ± 2.7 U/L). ALPL genetic testing, biochemical evaluations and assessment of clinical features by a systematic questionnaire among included patients, were performed. Results Among 24 participants, thirteen subjects (54.2%) revealed a disease-causing variant in ALPL and reported mild clinical features of HPP, of which musculoskeletal pain was the most frequently reported (n = 9). The variant c. 571G > A; p.(Glu191Lys) was identified in six subjects, and an unreported missense variant (c.1019A > C; p.(His340Pro)) as well as a deletion of exon 2 were detected by genetic screening. Biochemical analyses showed no significant differences in ALP (p = 0.059), the bone specific alkaline phosphatase (BALP) (p = 0.056) and pyridoxal-5′-phosphate (PLP) (p = 0.085) between patients with an ALPL variant and negative genetic screening. Patients with a variant in ALPL had significantly higher PLP levels than healthy controls (p = 0.002). We observed normal ALP activity in some patients classified as mild HPP, and slightly increased levels of PLP in two subjects with normal genetic screening and four healthy controls. Among 51 patients with persistent hypophosphatasaemia, fifteen subjects (29.4%) received antiresorptive treatment. Two patients with unrecognized HPP were treated with bisphosphonates and did not show complications due to the treatment. Conclusions Pathogenic variants in ALPL are common among patients with endocrinological diagnoses and low ALP. Regarding diagnostics, genetic testing is necessary to identify mild HPP due to fluctuating biochemical findings. Antiresorptive treatment is a frequent reason for hypophosphatasaemia and effects of these agents in adults with a variant in ALPL and osteoporosis remain unclear and require further studies. Mild HPP is overlooked among adults with endocrinological diagnoses. Biochemical hallmarks of HPP can fluctuate to normal among mild forms. Genetic screening of ALPL including MLPA is necessary to identify mild HPP. Musculoskeletal pain is the most common symptom in adult HPP. Effects of bisphosphonates in mild HPP need further studies.
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Affiliation(s)
- Nicola Hepp
- Dept. of Endocrinology, Hvidovre University Hospital Copenhagen, Kettegaard Alle 30, 2650 Hvidovre, Denmark
| | - Anja Lisbeth Frederiksen
- Dept. of Clinical Genetics, Aalborg University Hospital, Ladegaardsgade 5, 9000 Aalborg C, Denmark.,Dept. of Clinical Research, Aalborg University, Fredrik Bajers Vej 7K, 9220 Aalborg Ø, Denmark
| | - Morten Duno
- Dept. of Clinical Genetics, University Hospital Copenhagen Rigshospitalet, Blegdamsvej 9, 2100 Copenhagen, Denmark
| | - Jakob Præst Holm
- Department of Endocrinology, Copenhagen University Hospital Herlev, Borgmester Ib Juuls Vej 1, 2730 Herlev, Denmark
| | - Niklas Rye Jørgensen
- Dept. of Clinical Biochemistry, Rigshospitalet, Valdemar Hansens Vej 13, 2600 Glostrup, Denmark.,Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3 B, 2200 Copenhagen, Denmark
| | - Jens-Erik Beck Jensen
- Dept. of Endocrinology, Hvidovre University Hospital Copenhagen, Kettegaard Alle 30, 2650 Hvidovre, Denmark.,Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3 B, 2200 Copenhagen, Denmark
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23
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Jandl NM, Schmidt T, Rolvien T, Stürznickel J, Chrysostomou K, von Vopelius E, Volk AE, Schinke T, Kubisch C, Amling M, Barvencik F. Genotype-Phenotype Associations in 72 Adults with Suspected ALPL-Associated Hypophosphatasia. Calcif Tissue Int 2021; 108:288-301. [PMID: 33191482 PMCID: PMC7881968 DOI: 10.1007/s00223-020-00771-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Accepted: 10/12/2020] [Indexed: 12/11/2022]
Abstract
Hypophosphatasia (HPP) is a rare inborn error of metabolism due to a decreased activity of tissue nonspecific alkaline phosphatase (TNSALP). As the onset and severity of HPP are heterogenous, it can be challenging to determine the pathogenicity of detected rare ALPL variants in symptomatic patients. We aimed to characterize patients with rare ALPL variants to propose which patients can be diagnosed with adult HPP. We included 72 patients with (1) clinical symptoms of adult HPP or positive family history and (2) low TNSALP activity and/or high pyridoxal 5'-phosphate (PLP) levels, who underwent ALPL gene sequencing. The patients were analyzed and divided into three groups depending on ALPL variant pathogenicity according to the classification of the American College of Medical Genetics and Genomics (ACMG). Reported pathogenic (n = 34 patients), rare (n = 17) and common (n = 21) ALPL variants only were found. Muscular complaints were the most frequent symptoms (> 80%), followed by bone affection (> 50%). Tooth involvement was significantly more common in patients with pathogenic or rare ALPL variants. Seven rare variants could be classified as likely pathogenic (ACMG class 4) of which five have not yet been described. Inconclusive genetic findings and less specific symptoms make diagnosis difficult in cases where adult HPP is not obvious. As not every pathogenic or rare ALPL variant leads to a manifestation of HPP, only patients with bone complications and at least one additional complication concerning teeth, muscle, central nervous and mental system, repeated low TNSALP activity and high PLP levels should be diagnosed as adult HPP if rare ALPL gene variants of ACMG class 4 or higher support the diagnosis.
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Affiliation(s)
- Nico Maximilian Jandl
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Lottestrasse 59, 22529, Hamburg, Germany
- Department of Orthopedics, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, 20246, Hamburg, Germany
| | - Tobias Schmidt
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Lottestrasse 59, 22529, Hamburg, Germany
| | - Tim Rolvien
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Lottestrasse 59, 22529, Hamburg, Germany
- Department of Orthopedics, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, 20246, Hamburg, Germany
| | - Julian Stürznickel
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Lottestrasse 59, 22529, Hamburg, Germany
| | - Konstantin Chrysostomou
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Lottestrasse 59, 22529, Hamburg, Germany
| | - Emil von Vopelius
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Lottestrasse 59, 22529, Hamburg, Germany
- Department of Orthopedics, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, 20246, Hamburg, Germany
| | - Alexander E Volk
- Institute of Human Genetics, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, 20246, Hamburg, Germany
| | - Thorsten Schinke
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Lottestrasse 59, 22529, Hamburg, Germany
| | - Christian Kubisch
- Institute of Human Genetics, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, 20246, Hamburg, Germany
| | - Michael Amling
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Lottestrasse 59, 22529, Hamburg, Germany
| | - Florian Barvencik
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Lottestrasse 59, 22529, Hamburg, Germany.
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24
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Kato M, Hattori T, Shimizu T, Ninagawa K, Izumihara R, Nomoto H, Tanimura K, Atsumi T. Intrafamilial phenotypic distinction of hypophosphatasia with identical tissue nonspecific alkaline phosphatase gene mutation: a family report. J Bone Miner Metab 2020; 38:903-907. [PMID: 32772198 DOI: 10.1007/s00774-020-01137-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/18/2020] [Accepted: 07/30/2020] [Indexed: 10/23/2022]
Abstract
Hypophosphatasia (HPP) is caused by mutations in the tissue nonspecific alkaline phosphatase (TNSALP) gene in an autosomal recessive or dominant manner and characterized by defective mineralization of bone and low serum ALP levels. In this report, we present a family with HPP mother (case 1) and HPP child (case 2) who have identical TNSALP gene mutation (c.1015G>A p.Gly339Arg heterozygous mutation) but distinct clinical phenotypes. Whereas case 1 appeared to be asymptomatic despite extremely low levels of serum ALP, case 2 had several HPP-related symptoms, such as tooth loss, fractures, short stature, with slightly decreased ALP levels. Upon the diagnosis of HPP, case 1 discontinued denosumab, which was used to treat her rheumatoid arthritis, concerning the risk of atypical femoral fractures. The clinical course of this family was suggestive in a genotype-phenotype imbalance in HPP, the underdiagnosis of HPP in adults, and the risk of atypical femoral fractures using bone resorption inhibitors.
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Affiliation(s)
- Masaru Kato
- Department of Rheumatology, Endocrinology and Nephrology, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, N15W7, Kita-Ku, Sapporo, 060-8638, Japan.
| | | | - Tomohiro Shimizu
- Department of Orthopedic Surgery, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Sapporo, Japan
| | - Keita Ninagawa
- Department of Rheumatology, Endocrinology and Nephrology, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, N15W7, Kita-Ku, Sapporo, 060-8638, Japan
| | - Rimi Izumihara
- Department of Rheumatology, Endocrinology and Nephrology, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, N15W7, Kita-Ku, Sapporo, 060-8638, Japan
| | - Hiroshi Nomoto
- Department of Rheumatology, Endocrinology and Nephrology, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, N15W7, Kita-Ku, Sapporo, 060-8638, Japan
| | | | - Tatsuya Atsumi
- Department of Rheumatology, Endocrinology and Nephrology, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, N15W7, Kita-Ku, Sapporo, 060-8638, Japan
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25
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Huggins E, Ong R, Rockman-Greenberg C, Flueckinger LB, Dahir KM, Kishnani PS. Multigenerational case examples of hypophosphatasia: Challenges in genetic counseling and disease management. Mol Genet Metab Rep 2020; 25:100661. [PMID: 33101980 PMCID: PMC7578550 DOI: 10.1016/j.ymgmr.2020.100661] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Revised: 10/05/2020] [Accepted: 10/06/2020] [Indexed: 12/19/2022] Open
Abstract
Hypophosphatasia (HPP) is an inherited metabolic condition caused by pathogenic mutations in the ALPL gene. This leads to deficiency of tissue non-specific alkaline phosphatase (TNSALP), resulting in decreased mineralization of the bones and/or teeth and multi-systemic complications. Inheritance may be autosomal dominant or recessive, and the phenotypic spectrum, including age of onset, varies widely. We present four families demonstrating both modes of inheritance of HPP and phenotypic variability and discuss the resultant challenges in disease management, genetic counseling, and risk assessment. Failure to consider different modes of inheritance in a family with HPP may lead to an inaccurate risk assessment upon which medical and reproductive decisions may be made. We highlight the essential role of high-quality genetic counseling and meaningful biochemical and molecular testing strategies in the evaluation and management of families with HPP.
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Affiliation(s)
- Erin Huggins
- Division of Medical Genetics, Department of Pediatrics, Duke University Medical Center, Durham, NC, USA
| | - Ricardo Ong
- Division of Medical Genetics, Department of Pediatrics, Duke University Medical Center, Durham, NC, USA
| | - Cheryl Rockman-Greenberg
- Department of Pediatrics and Child Health, Max Rady College of Medicine, University of Manitoba, Winnipeg, MB, Canada
| | - Lauren Bailey Flueckinger
- Division of Medical Genetics, Department of Pediatrics, Duke University Medical Center, Durham, NC, USA
| | - Kathryn M Dahir
- Vanderbilt University Medical Center, Program for Metabolic Bone Disorders, Division of Endocrinology, Nashville, TN, USA
| | - Priya S Kishnani
- Division of Medical Genetics, Department of Pediatrics, Duke University Medical Center, Durham, NC, USA
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26
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Mornet E, Taillandier A, Domingues C, Dufour A, Benaloun E, Lavaud N, Wallon F, Rousseau N, Charle C, Guberto M, Muti C, Simon-Bouy B. Hypophosphatasia: a genetic-based nosology and new insights in genotype-phenotype correlation. Eur J Hum Genet 2020; 29:289-299. [PMID: 32973344 DOI: 10.1038/s41431-020-00732-6] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2019] [Revised: 09/08/2020] [Accepted: 09/15/2020] [Indexed: 11/09/2022] Open
Abstract
Hypophosphatasia (HPP) is caused by pathogenic variants in the ALPL gene. There is a large continuum in the severity, ranging from a lethal perinatal form to dental issues. We analyzed a cohort of 424 HPP patients from European geographic origin or ancestry. Using 3D modeling and results of functional tests we classified ALPL pathogenic variants according to their dominant negative effect (DNE) and their severity. The cohort was described by the genotypes resulting from alleles s (severe recessive), Sd (severe dominant), and m (moderate). Many recurrent variants showed a regional anchor pointing out founder effects rather than multiple mutational events. Homozygosity was an aggravating factor of the severity and moderate alleles were rare both in number and frequency. Pathogenic variants with DNE were found in both recessive and dominant HPP. Sixty percent of the adults tested were heterozygous for a variant showing no DNE, suggesting another mechanism of dominance like haploinsufficiency. Adults with dominant HPP without DNE were found statistically less severely affected than adults with DNE variants. Adults with dominant HPP without DNE represent a new clinical entity mostly diagnosed from 2010s, characterized by nonspecific signs of HPP and low alkaline phosphatase, and for which a high prevalence is expected. In conclusion, the genetic composition of our cohort suggests a nosology with 3 clinical forms: severe HPP is recessive and rare, moderate HPP is recessive or dominant and more common, and mild HPP, characterized by low alkaline phosphatase and unspecific clinical signs, is dominantly inherited and very common.
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Affiliation(s)
- Etienne Mornet
- Unité de Génétique Constitutionnelle, Service de Biologie, Centre Hospitalier de Versailles, 78150, Le Chesnay, France.
| | - Agnès Taillandier
- Unité de Génétique Constitutionnelle, Service de Biologie, Centre Hospitalier de Versailles, 78150, Le Chesnay, France
| | - Christelle Domingues
- Unité de Génétique Constitutionnelle, Service de Biologie, Centre Hospitalier de Versailles, 78150, Le Chesnay, France
| | - Annika Dufour
- Unité de Génétique Constitutionnelle, Service de Biologie, Centre Hospitalier de Versailles, 78150, Le Chesnay, France
| | - Emmanuelle Benaloun
- Unité de Génétique Constitutionnelle, Service de Biologie, Centre Hospitalier de Versailles, 78150, Le Chesnay, France
| | - Nicole Lavaud
- Unité de Génétique Constitutionnelle, Service de Biologie, Centre Hospitalier de Versailles, 78150, Le Chesnay, France
| | - Fabienne Wallon
- Unité de Génétique Constitutionnelle, Service de Biologie, Centre Hospitalier de Versailles, 78150, Le Chesnay, France
| | - Nathalie Rousseau
- Unité de Génétique Constitutionnelle, Service de Biologie, Centre Hospitalier de Versailles, 78150, Le Chesnay, France
| | - Carole Charle
- Unité de Génétique Constitutionnelle, Service de Biologie, Centre Hospitalier de Versailles, 78150, Le Chesnay, France
| | - Mihelaiti Guberto
- Unité de Génétique Constitutionnelle, Service de Biologie, Centre Hospitalier de Versailles, 78150, Le Chesnay, France
| | - Christine Muti
- Unité de Génétique Constitutionnelle, Service de Biologie, Centre Hospitalier de Versailles, 78150, Le Chesnay, France
| | - Brigitte Simon-Bouy
- Unité de Génétique Constitutionnelle, Service de Biologie, Centre Hospitalier de Versailles, 78150, Le Chesnay, France
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27
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Li XY, Wan XH, Chen L, Guo WH, Wang L. A compound heterozygous ALPL variant in a patient with dystonia-parkinsonism and hypointensity in basal ganglia: A case report. Parkinsonism Relat Disord 2020; 78:184-185. [PMID: 32956941 DOI: 10.1016/j.parkreldis.2020.07.027] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Revised: 07/20/2020] [Accepted: 07/29/2020] [Indexed: 11/17/2022]
Affiliation(s)
- Xin-Yao Li
- Department of Neurology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, 100730, China
| | - Xin-Hua Wan
- Department of Neurology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, 100730, China
| | - Lin Chen
- Department of Neurology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, 100730, China
| | - Wei-Hong Guo
- Department of Vasculocardiology, Fuwai Hospital, Chinese Academy of Medical Sciences, 100037, China
| | - Lin Wang
- Department of Neurology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, 100730, China.
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28
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Tilden DR, Sheehan JH, Newman JH, Meiler J, Capra JA, Ramirez A, Simmons J, Dahir K. Phenotypic Profiling in Subjects Heterozygous for 1 of 2 Rare Variants in the Hypophosphatasia Gene ( ALPL). J Endocr Soc 2020; 4:bvaa084. [PMID: 32803091 PMCID: PMC7417882 DOI: 10.1210/jendso/bvaa084] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/11/2020] [Accepted: 06/22/2020] [Indexed: 11/19/2022] Open
Abstract
Context Hypophosphatasia (HPP) is a syndrome marked by low serum alkaline phosphatase (AlkP) activity as well as musculoskeletal and/or dental disease. While the majority of subjects with HPP carry a pathogenic variant in the ALPL gene or its regulatory regions, individual pathogenic variants are often not tightly correlated with clinical symptomatology. We sought to better understand the genotype/phenotype correlation in HPP by examining the clinical and biochemical data of 37 subjects with 2 rare variants in ALPL. Methods Through BioVU, a DNA biobank that pairs individuals’ genetic information with their de-identified medical records, we identified subjects with 2 rare variants with distinct reported clinical phenotypes (p.D294A and p.T273M). We then performed a manual review of these subjects’ de-identified medical records along with computational modeling of protein structure to construct a genetic, biochemical and clinical phenotype for each subject and variant. Results Twenty subjects with the p.D294A variant and 17 with the p.T273M variant had sufficient data for analysis. Among subjects in our cohort with the p.D294A variant, 6 (30.0%) had both clinical bone disease and serum AlkP activity below 40 IU/L while 4 subjects (23.5%) with the p.T273M variant met the same criteria despite the distinct clinical phenotypes of these variants. Conclusions Given the loose genotype/phenotype correlation in HPP seen in our cohort, clinical context is crucial for the interpretation of genetic test results to guide clinical care in this population. Otherwise, over- or under-diagnosis may occur, resulting in misidentification of those who may benefit from additional screening and perhaps pharmacologic intervention.
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Affiliation(s)
- Daniel R Tilden
- Division of Endocrinology, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee.,Ian M. Burr Division of Pediatric Endocrinology, Department of Pediatrics, Monroe Carroll Jr. Children's Hospital at Vanderbilt, Nashville, Tennessee
| | - Jonathan H Sheehan
- Division of Infectious Diseases, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri
| | - John H Newman
- Division of Allergy, Pulmonary and Critical Care Medicine, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Jens Meiler
- Center for Structural Biology, Vanderbilt University Medical Center Nashville, TN.,Department of Chemistry, Vanderbilt University Medical Center, Nashville, Tennessee.,Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee
| | - John A Capra
- Center for Structural Biology, Vanderbilt University Medical Center Nashville, TN.,Department of Chemistry, Vanderbilt University Medical Center, Nashville, Tennessee.,Department of Biological Sciences and Biomedical Informatics, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Andrea Ramirez
- Division of Endocrinology, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Jill Simmons
- Ian M. Burr Division of Pediatric Endocrinology, Department of Pediatrics, Monroe Carroll Jr. Children's Hospital at Vanderbilt, Nashville, Tennessee
| | - Kathryn Dahir
- Division of Endocrinology, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee
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29
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del Angel G, Reynders J, Negron C, Steinbrecher T, Mornet E. Large-scale in vitro functional testing and novel variant scoring via protein modeling provide insights into alkaline phosphatase activity in hypophosphatasia. Hum Mutat 2020; 41:1250-1262. [PMID: 32160374 PMCID: PMC7317754 DOI: 10.1002/humu.24010] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Revised: 02/05/2020] [Accepted: 03/04/2020] [Indexed: 01/20/2023]
Abstract
Hypophosphatasia (HPP) is a rare metabolic disorder characterized by low tissue‐nonspecific alkaline phosphatase (TNSALP) typically caused by ALPL gene mutations. HPP is heterogeneous, with clinical presentation correlating with residual TNSALP activity and/or dominant‐negative effects (DNE). We measured residual activity and DNE for 155 ALPL variants by transient transfection and TNSALP enzymatic activity measurement. Ninety variants showed low residual activity and 24 showed DNE. These results encompass all missense variants with carrier frequencies above 1/25,000 from the Genome Aggregation Database. We used resulting data as a reference to develop a new computational algorithm that scores ALPL missense variants and predicts high/low TNSALP enzymatic activity. Our approach measures the effects of amino acid changes on TNSALP dimer stability with a physics‐based implicit solvent energy model. We predict mutation deleteriousness with high specificity, achieving a true‐positive rate of 0.63 with false‐positive rate of 0, with an area under receiver operating curve (AUC) of 0.9, better than all in silico predictors tested. Combining this algorithm with other in silico approaches can further increase performance, reaching an AUC of 0.94. This study expands our understanding of HPP heterogeneity and genotype/phenotype relationships with the aim of improving clinical ALPL variant interpretation.
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Affiliation(s)
- Guillermo del Angel
- Data Sciences, Genomics, and BioinformaticsAlexion Pharmaceuticals, Inc.BostonMassachusetts
| | - John Reynders
- Data Sciences, Genomics, and BioinformaticsAlexion Pharmaceuticals, Inc.BostonMassachusetts
| | | | | | - Etienne Mornet
- Laboratoire de Génétique Constitutionnelle Prénatale et PostnataleCentre Hospitalier de VersaillesLe ChesnayFrance
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