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Portale AA, Ward L, Dahir K, Florenzano P, Ing SW, Jan de Beur SM, Martin RM, Meza-Martinez AI, Paloian N, Ashraf A, Dixon BP, Khan A, Langman C, Chen A, Wang C, Roberts MS, Tandon PK, Bedrosian C, Imel EA. Nephrocalcinosis and kidney function in children and adults with X-linked hypophosphatemia: baseline results from a large longitudinal study. J Bone Miner Res 2024; 39:1493-1502. [PMID: 39151033 PMCID: PMC11425691 DOI: 10.1093/jbmr/zjae127] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/17/2024] [Revised: 07/09/2024] [Accepted: 07/17/2024] [Indexed: 08/18/2024]
Abstract
BACKGROUND In patients with X-linked hypophosphatemia (XLH), conventional therapy with oral phosphate salts and active vitamin D has been associated with nephrocalcinosis. However, the nature of the relationships among XLH, its treatment, nephrocalcinosis, and kidney function remain poorly understood. METHODS Renal ultrasounds were performed and glomerular filtration rates were estimated (eGFR) at baseline in burosumab-naïve patients with XLH who participated in burosumab clinical trials (NCT02181764, NCT02526160, NCT02537431, NCT02163577, NCT02750618, NCT02915705) or enrolled in the XLH Disease Monitoring Program (XLH-DMP; NCT03651505). In this cross-sectional analysis, patient, disease, and treatment characteristics were described among patients with and without nephrocalcinosis. RESULTS The analysis included 196 children (mean [SD] age 7.6 [4.0] yr) and 318 adults (40.3 [13.1] yr). Mean (SD) height z-score was -1.9 (1.2) for children and -2.3 (1.7) for adults. Nearly all children (97%) and adults (94%) had previously received conventional therapy. Nephrocalcinosis was detected in 22% of children and 38% of adults. In children, reduced eGFR <90 mL/min/1.73 m2 was more prevalent in those with nephrocalcinosis (25%) than in those without (11%), a finding that was not observed in adults. Children with nephrocalcinosis had lower mean values of TmP/GFR (p<.05), serum 1,25(OH)2D (p<.05), and eGFR (p<.001) and higher mean serum calcium concentrations (p<.05) than did those without nephrocalcinosis. Adults with nephrocalcinosis had lower mean serum phosphorus (p<.01) and 1,25(OH)2D (p<.05) concentrations than those without. Exploratory logistic regression analyses revealed no significant associations between the presence of nephrocalcinosis and other described patient or disease characteristics. CONCLUSIONS Nephrocalcinosis was observed in nearly one-quarter of children and more than one-third of adults with XLH. Further study is needed to better understand the predictors and long-term consequences of nephrocalcinosis, with surveillance for nephrocalcinosis remaining important in the management of XLH.
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Affiliation(s)
- Anthony A Portale
- Division of Pediatric Nephrology, University of California San Francisco Benioff Children’s Hospital, San Francisco, CA 94158, United States
| | - Leanne Ward
- Department of Pediatrics, University of Ottawa, Children's Hospital of Eastern Ontario, Ottawa, Ontario, ON K1H 8L1, Canada
| | - Kathryn Dahir
- Vanderbilt University Medical Center, Nashville, TN 37232, United States
| | - Pablo Florenzano
- Department of Endocrinology, Faculty of Medicine, Pontificia Universidad Católica de Chile and Centro UC Traslacional en Endocrinología, CETREN-UC, 8320165 Santiago, Chile
| | - Steven W Ing
- Division of Endocrinology, Diabetes, and Metabolism, Ohio State University Wexner Medical Center, Columbus, OH 43210, United States
| | - Suzanne M Jan de Beur
- Division of Endocrinology and Metabolism, Department of Medicine, University of Virginia School of Medicine, Charlotteville, VA 22903, United States
| | - Regina M Martin
- Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo, Sao Paulo 05403-010, Brazil
| | | | - Neil Paloian
- University of Wisconsin School of Medicine and Public Health, Madison, WI 53726, United States
| | - Ambika Ashraf
- University of Alabama at Birmingham, Birmingham, AL 35294, United States
| | - Bradley P Dixon
- Renal Section, Department of Pediatrics, University of Colorado School of Medicine, Aurora, CO 80045, United States
| | - Aliya Khan
- McMaster University, Hamilton, Ontario L8S 4L8, Canada
| | - Craig Langman
- Emeritus Professor of Pediatrics, Northwestern Feinberg School of Medicine, Chicago, IL 60611, United States
| | - Angel Chen
- Ultragenyx Pharmaceutical Inc., Novato, CA 94949, United States
| | - Christine Wang
- Ultragenyx Pharmaceutical Inc., Novato, CA 94949, United States
| | | | - P K Tandon
- Ultragenyx Pharmaceutical Inc., Novato, CA 94949, United States
| | | | - Erik A Imel
- Indiana University School of Medicine, Indianapolis, IN 46202, United States
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2
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Kamenický P, Briot K, Munns CF, Linglart A. X-linked hypophosphataemia. Lancet 2024; 404:887-901. [PMID: 39181153 DOI: 10.1016/s0140-6736(24)01305-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/17/2023] [Revised: 06/17/2024] [Accepted: 06/18/2024] [Indexed: 08/27/2024]
Abstract
X-linked hypophosphataemia is a genetic disease caused by defects in the phosphate regulating endopeptidase homolog X-linked (PHEX) gene and is characterised by X-linked dominant inheritance. The main consequence of PHEX deficiency is increased production of the phosphaturic hormone fibroblast growth factor 23 (FGF23) in osteoblasts and osteocytes. Chronic exposure to circulating FGF23 is responsible for renal phosphate wasting and decreased synthesis of calcitriol, which decreases intestinal phosphate absorption. These mechanisms result in lifelong hypophosphataemia, impaired growth plate and bone matrix mineralisation, and diverse manifestations in affected children and adults, including some debilitating morbidities and possibly increased mortality. Important progress has been made in disease knowledge and management over the past decade; in particular, targeting FGF23 is a therapeutic approach that has substantially improved outcomes. However, patients affected by this complex disease need lifelong care and innovative treatment strategies, such as gene repair of PHEX, are necessary to further limit the disease burden.
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Affiliation(s)
- Peter Kamenický
- Université Paris-Saclay, Inserm, Physiologie et Physiopathologie Endocriniennes, Le Kremlin-Bicêtre, France; Centre de Référence des Maladies du Métabolisme du Calcium et du Phosphate, Service d'Endocrinologie et des Maladies de la Reproduction, Hôpital Bicêtre, Assistance Publique-Hôpitaux de Paris, Le Kremlin-Bicêtre, France.
| | - Karine Briot
- Centre de Référence des Maladies du Métabolisme du Calcium et du Phosphate, Service de Rhumatologie, Hôpital Cochin, Assistance Publique-Hôpitaux de Paris, Paris, France
| | - Craig F Munns
- Department of Endocrinology and Diabetes, Queensland Children's Hospital and Child Health Research Centre and Faculty of Medicine, The University of Queensland, Brisbane, QLD, Australia
| | - Agnès Linglart
- Université Paris-Saclay, Inserm, Physiologie et Physiopathologie Endocriniennes, Le Kremlin-Bicêtre, France; Service d'Endocrinologie et du Diabète de l'Enfant, Hôpital Bicêtre, Assistance Publique-Hôpitaux de Paris, Le Kremlin-Bicêtre, France
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3
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Puente N, Solis P, Riancho JA. Genetic causes of hypophosphatemia. Minerva Med 2024; 115:320-336. [PMID: 38727708 DOI: 10.23736/s0026-4806.24.09198-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/21/2024]
Abstract
Phosphate is a key component of mineralized tissues and is also part of many organic compounds. Phosphorus homeostasis depends especially upon intestinal absorption, and renal excretion, which are regulated by various hormones, such as PTH, 1,25-dihydroxyvitamin D, and fibroblast growth factor 23. In this review we provide an update of several genetic disorders that affect phosphate transporters through cell membranes or the phosphate-regulating hormones, and, consequently, result in hypophosphatemia.
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Affiliation(s)
- Nuria Puente
- Service of Internal Medicine, Hospital U. M. Valdecilla, University of Cantabria, Santander, Spain
- Department of Medicine and Psychiatry, University of Cantabria, Santander, Spain
- Valdecilla Research Institute, Santander, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER, ISCIII), Madrid, Spain
| | - Pablo Solis
- Service of Internal Medicine, Hospital U. M. Valdecilla, University of Cantabria, Santander, Spain
| | - Jose A Riancho
- Service of Internal Medicine, Hospital U. M. Valdecilla, University of Cantabria, Santander, Spain -
- Department of Medicine and Psychiatry, University of Cantabria, Santander, Spain
- Valdecilla Research Institute, Santander, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER, ISCIII), Madrid, Spain
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4
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Pan F, Zhang R, Liu X, Shi X, Xin Q, Qiao D, Li C, Zhang Y, Chen M, Guo W, Luan S, Shao L. Three exonic variants in the PHEX gene cause aberrant splicing in a minigene assay. Front Genet 2024; 15:1353674. [PMID: 38841723 PMCID: PMC11150636 DOI: 10.3389/fgene.2024.1353674] [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: 12/11/2023] [Accepted: 04/24/2024] [Indexed: 06/07/2024] Open
Abstract
Background: X-linked hypophosphatemia (XLH, OMIM 307800) is a rare phosphorus metabolism disorder caused by PHEX gene variants. Many variants simply classified as missense or nonsense variants were only analyzed at the DNA level. However, growing evidence indicates that some of these variants may alter pre-mRNA splicing, causing diseases. Therefore, this study aimed to use bioinformatics tools and a minigene assay to ascertain the effects of PHEX variations on pre-mRNA splicing. Methods: We analyzed 174 variants in the PHEX gene described as missense or nonsense variants. Finally, we selected eight candidate variants using bioinformatics tools to evaluate their effects on pre-mRNA splicing using a minigene assay system. The complementary DNA (cDNA) sequence for the PHEX gene (RefSeq NM_000444.6) serves as the basis for DNA variant numbering. Results: Of the eight candidate variants, three were found to cause abnormal splicing. Variants c.617T>G p.(Leu206Trp) and c.621T>A p.(Tyr207*) in exon 5 altered the splicing of pre-mRNA, owing to the activation of a cryptic splice site in exon 5, which produced an aberrant transcript lacking a part of exon 5, whereas variant c.1700G>C p.(Arg567Pro) in exon 16 led to the activation of a cryptic splice site in intron 16, resulting in a partial inclusion of intron 16. Conclusion: Our study employed a minigene system, which has a great degree of flexibility to assess abnormal splicing patterns under the circumstances of patient mRNA samples that are not available, to explore the impact of the exonic variants on pre-mRNA splicing. Based on the aforementioned experimental findings, we demonstrated the importance of analyzing exonic variants at the mRNA level.
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Affiliation(s)
- Fengjiao Pan
- Department of Nephrology, The Affiliated Qingdao Municipal Hospital of Qingdao University, Qingdao, China
| | - Ruixiao Zhang
- Department of Emergency, The Affiliated Qingdao Municipal Hospital of Qingdao University, Qingdao, China
| | - Xuyan Liu
- Department of Nephrology, The Affiliated Qingdao Municipal Hospital of Qingdao University, Qingdao, China
| | - Xiaomeng Shi
- Department of Nephrology, The Affiliated Qingdao Municipal Hospital of Qingdao University, Qingdao, China
| | - Qing Xin
- Department of Nephrology, The Affiliated Qingdao Municipal Hospital of Qingdao University, Qingdao, China
- Department of Nephrology, The Key Laboratory for the Prevention and Treatment of Chronic Kidney Disease of Chongqing, Chongqing Clinical Research Center of Kidney and Urology Diseases, Xinqiao Hospital, Army Medical University (Third Military Medical University), Chongqing, China
| | - Dan Qiao
- Department of Nephrology, Dalian Medical University, Dalian, China
| | - Changying Li
- Department of Nephrology, The Affiliated Qingdao Municipal Hospital of Qingdao University, Qingdao, China
| | - Yan Zhang
- Department of Nephrology, Weifang Medical University, Weifang, China
| | - Mengke Chen
- Department of Nephrology, Liaocheng Third People’s Hospital, Liaocheng, China
| | - Wencong Guo
- Department of Nephrology, The Affiliated Qingdao Municipal Hospital of Qingdao University, Qingdao, China
- Institute of Nephrology, Zhong Da Hospital, Southeast University School of Medicine, Nanjing, China
| | - Shufang Luan
- Department of Medical Insurance Administration, The Affiliated Qingdao Municipal Hospital of Qingdao University, Qingdao, China
| | - Leping Shao
- Department of Nephrology, The Affiliated Qingdao Municipal Hospital of Qingdao University, Qingdao, China
- Department of Nephrology, The First Affiliated Hospital of Xiamen University, Xiamen, China
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5
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Nakanishi T, Yamazaki M, Tachikawa K, Ueta A, Kawai M, Ozono K, Michigami T. Complex intrinsic abnormalities in osteoblast lineage cells of X-linked hypophosphatemia: Analysis of human iPS cell models generated by CRISPR/Cas9-mediated gene ablation. Bone 2024; 181:117044. [PMID: 38331306 DOI: 10.1016/j.bone.2024.117044] [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: 11/16/2023] [Revised: 01/04/2024] [Accepted: 02/05/2024] [Indexed: 02/10/2024]
Abstract
X-linked hypophosphatemia (XLH) is caused by inactivating variants of the phosphate regulating endopeptidase homolog X-linked (PHEX) gene. Although the overproduction of fibroblast growth factor 23 (FGF23) is responsible for hypophosphatemia and impaired vitamin D metabolism, the pathogenesis of XLH remains unclear. We herein generated PHEX-knockout (KO) human induced pluripotent stem (iPS) cells by applying CRISPR/Cas9-mediated gene ablation to an iPS clone derived from a healthy male, and analyzed PHEX-KO iPS cells with deletions extending from exons 1 to 3 and frameshifts by inducing them to differentiate into the osteoblast lineage. We confirmed the increased production of FGF23 in osteoblast lineage cells differentiated from PHEX-KO iPS cells. In vitro mineralization was enhanced in osteoblast lineage cells from PHEX-KO iPS cells than in those from isogenic control iPS cells, which reminded us of high bone mineral density and enthesopathy in patients with XLH. The extracellular level of pyrophosphate (PPi), an inhibitor of mineralization, was elevated, and this increase appeared to be partly due to the reduced activity of tissue non-specific alkaline phosphatase (TNSALP). Osteoblast lineage cells derived from PHEX-KO iPS cells also showed the increased expression of multiple molecules such as dentine matrix protein 1, osteopontin, RUNX2, FGF receptor 1 and early growth response 1. This gene dysregulation was similar to that in the osteoblasts/osteocytes of Phex-deficient Hyp mice, suggesting that common pathogenic mechanisms are shared between human XLH and Hyp mice. Moreover, we found that the phosphorylation of CREB was markedly enhanced in osteoblast lineage cells derived from PHEX-KO iPS cells, which appeared to be associated with the up-regulation of the parathyroid hormone related protein gene. PHEX deficiency also affected the response of the ALPL gene encoding TNSALP to extracellular Pi. Collectively, these results indicate that complex intrinsic abnormalities in osteoblasts/osteocytes underlie the pathogenesis of human XLH.
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Affiliation(s)
- Tatsuro Nakanishi
- Department of Bone and Mineral Research, Research Institute, Osaka Women's and Children's Hospital, Osaka Prefectural Hospital Organization, Izumi, Osaka 594-1101, Japan; Department of Pediatrics, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan
| | - Miwa Yamazaki
- Department of Bone and Mineral Research, Research Institute, Osaka Women's and Children's Hospital, Osaka Prefectural Hospital Organization, Izumi, Osaka 594-1101, Japan
| | - Kanako Tachikawa
- Department of Bone and Mineral Research, Research Institute, Osaka Women's and Children's Hospital, Osaka Prefectural Hospital Organization, Izumi, Osaka 594-1101, Japan
| | - Ayu Ueta
- Department of Bone and Mineral Research, Research Institute, Osaka Women's and Children's Hospital, Osaka Prefectural Hospital Organization, Izumi, Osaka 594-1101, Japan; 1st Department of Oral and Maxillofacial Surgery, Osaka University Graduate School of Dentistry, Suita, Osaka 565-0871, Japan
| | - Masanobu Kawai
- Department of Bone and Mineral Research, Research Institute, Osaka Women's and Children's Hospital, Osaka Prefectural Hospital Organization, Izumi, Osaka 594-1101, Japan
| | | | - Toshimi Michigami
- Department of Bone and Mineral Research, Research Institute, Osaka Women's and Children's Hospital, Osaka Prefectural Hospital Organization, Izumi, Osaka 594-1101, Japan.
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Bartels K, Afonso S, Brown L, Carriles C, Kim R, Lazier J, Mercimek-Andrews S, Nelson TN, Stedman I, Thain E, Vanneste R, Chad L. Next generation of free? Points to consider when navigating sponsored genetic testing. J Med Genet 2024; 61:299-304. [PMID: 37932018 DOI: 10.1136/jmg-2023-109571] [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: 08/10/2023] [Accepted: 09/28/2023] [Indexed: 11/08/2023]
Abstract
Genetics has been integrated into patient care across many subspecialties. However, genetic and genomic testing (GT) remain expensive with disparities in access both within Canada and internationally. It is, therefore, not surprising that sponsored GT has emerged as one alternative. Sponsored GT, for the purpose of this document, refers to clinical-grade GT partially or fully subsidised by industry. In return, industry sponsors-usually pharmaceutical or biotechnology companies-may have access to patients' genetic data, practitioner information, DNA and/or other information. The availability of sponsored GT options in the Canadian healthcare landscape has appeared to simplify patient and practitioner access to GT, but the potential ethical and legal considerations, as well as the nuances of a publicly funded healthcare system, must also be considered. This document offers preliminary guidance for Canadian healthcare practitioners encountering sponsored GT in practice. Further research and dialogue is urgently needed to explore this issue to provide fulsome considerations that one must be aware of when availing such options.
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Affiliation(s)
- Kirsten Bartels
- Department of Medicine, Providence Health Care Heart Centre, St. Paul's Hospital, Vancouver, British Columbia, Canada
| | - Samantha Afonso
- Heart, Lung and Vascular Program, St. Michael's Hospital, Unity Health Toronto, Toronto, Ontario, Canada
| | - Lindsay Brown
- Pathology & Laboratory Medicine, BC Children's Hospital, Vancouver, British Columbia, Canada
| | - Claudia Carriles
- Genomics Laboratory, Shared Health Manitoba, Winnipeg, Manitoba, Canada
| | - Raymond Kim
- Department of Medicine, Division of Medical Oncology and Hematology, Princess Margaret Cancer Centre, University Health Network, Toronto, Ontario, Canada
| | - Joanna Lazier
- Medical Genetics, Children's Hospital of Eastern Ontario, Ottawa, Ontario, Canada
| | | | - Tanya N Nelson
- Pathology & Laboratory Medicine, BC Children's Hospital, Vancouver, British Columbia, Canada
| | - Ian Stedman
- School of Public Policy and Administration, York University, Toronto, Ontario, Canada
| | - Emily Thain
- Familial Cancer Clinic, University Health Network, Toronto, Ontario, Canada
| | - Rachel Vanneste
- Division of Medical Genetics, Department of Pediatrics, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Lauren Chad
- Department of Pediatrics, The Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Bioethics, The Hospital for Sick Children, Toronto, Ontario, Canada
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Fourikou M, Karipiadou A, Ververi A, Savvidou P, Laliotis N, Tsitouras V, Stabouli S, Roilides E, Kollios K. X-linked hypophosphatemia due to a de novo novel splice-site variant in a 7-year-old girl with scaphocephaly, Chiari syndrome type I and syringomyelia. Bone Rep 2024; 20:101731. [PMID: 38226334 PMCID: PMC10788211 DOI: 10.1016/j.bonr.2023.101731] [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: 08/24/2023] [Revised: 12/09/2023] [Accepted: 12/12/2023] [Indexed: 01/17/2024] Open
Abstract
X-linked hypophosphatemia (XLH) is a rare X-linked dominant inherited disorder caused by loss-of-function variants in the PHEX gene and characterized by renal phosphate wasting, hypophosphatemia, abnormal vitamin D metabolism, growth retardation and lower limb deformities. We describe a case of XLH-rickets in a 7-year-old girl with scaphocephaly, Chiari syndrome type I and syringomyelia, with a de novo non-canonical splice variant (c.1080-3C > G) in intron 9 of the PHEX gene, that has not been previously described.
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Affiliation(s)
- Maria Fourikou
- 3rd Department of Paediatrics, Aristotle University of Thessaloniki, Hippokration General Hospital, Konstantinoupoleos 49, 54642 Thessaloniki, Greece
| | - Aristea Karipiadou
- 3rd Department of Paediatrics, Aristotle University of Thessaloniki, Hippokration General Hospital, Konstantinoupoleos 49, 54642 Thessaloniki, Greece
| | - Athina Ververi
- Centre for Genetics of Rare Diseases, Papageorgiou General Hospital, Agiou Pavlou 76, Pavlos Melas 564 29, Thessaloniki, Greece
| | - Parthena Savvidou
- 3rd Department of Paediatrics, Aristotle University of Thessaloniki, Hippokration General Hospital, Konstantinoupoleos 49, 54642 Thessaloniki, Greece
| | - Nikolaos Laliotis
- Department of Orthopaedics, Inter Balkan Medical Center, Asklipiou 10, 57001 Pylaia, Thessaloniki, Greece
| | - Vassilios Tsitouras
- 2nd Neurosurgery Department, Aristotle University of Thessaloniki, Hippokration General Hospital, Konstantinoupoleos 49, 54642 Thessaloniki, Greece
| | - Stella Stabouli
- 1st Department of Paediatrics, Aristotle University of Thessaloniki, Hippokration General Hospital, Konstantinoupoleos 49, 54642 Thessaloniki, Greece
| | - Emmanuel Roilides
- 3rd Department of Paediatrics, Aristotle University of Thessaloniki, Hippokration General Hospital, Konstantinoupoleos 49, 54642 Thessaloniki, Greece
| | - Konstantinos Kollios
- 3rd Department of Paediatrics, Aristotle University of Thessaloniki, Hippokration General Hospital, Konstantinoupoleos 49, 54642 Thessaloniki, Greece
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8
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Vaisbich MH, de Cillo ACP, Silva BCC, DÁlva CB, de Carvalho ÉH, de Almeida JMCM, Marques LLM, Ribeiro M, da Silva MBM, de Medeiros PFV, Mendes PH. Real-world data of Brazilian adults with X-linked hypophosphatemia (XLH) treated with burosumab and comparison with other worldwide cohorts. Mol Genet Genomic Med 2024; 12:e2387. [PMID: 38337160 PMCID: PMC10858313 DOI: 10.1002/mgg3.2387] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Revised: 12/23/2023] [Accepted: 01/17/2024] [Indexed: 02/12/2024] Open
Abstract
BACKGROUND Disease-related variants in PHEX cause XLH by an increase of fibroblast growth factor 23 (FGF23) circulating levels, resulting in hypophosphatemia and 1,25(OH)2 vitamin D deficiency. XLH manifests in early life with rickets and persists in adulthood with osseous and extraosseous manifestations. Conventional therapy (oral phosphate and calcitriol) improves some symptoms, but evidence show that it is not completely effective, and it can lead to nephrocalcinosis (NC) and hyperparathyroidism (HPT). Burosumab (anti-FGF23 antibody) has shown to be effective and safety in the clinical trials. METHODS The current real-world collaborative study evaluated genetic, clinical and laboratory data of XLH Brazilian adult patients treated with burosumab. RESULTS Nineteen unrelated patients were studied. Patients reported pain, limb deformities and claudication, before burosumab initiation. 78% of them were previously treated with conventional therapy. The severity of the disease was moderate to severe (15 patients with score >5). At the baseline, 3 patients presented NC (16.7%) and 12 HPT (63%). After 16 ± 8.4 months under burosumab, we observed a significant: increase in stature (p = 0.02), in serum phosphate from 1.90 ± 0.43 to 2.67 ± 0.52 mg/dL (p = 0.02); in TmP/GFR from 1.30 ± 0.46 to 2.27 ± 0.64 mg/dL (p = 0.0001), in 1,25 (OH)2 D from 50.5 ± 23.3 to 71.1 ± 19.1 pg/mL (p = 0.03), and a decrease in iPTH from 86.8 ± 37.4 pg/mL to 66.5 ± 31.1 (p = 0.002). Nineteen variants were found (10 novel). HPT tended to develop in patients with truncated PHEX variants (p = 0.06). CONCLUSIONS This study confirms the efficacy and safety of burosumab on XLH adult patients observed in clinical trials. Additionally, we observed a decrease in iPTH levels in patients with moderate to severe HPT at the baseline.
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Affiliation(s)
| | | | - Bárbara Campolina C. Silva
- Hospital Felício Rocho, Osteometabolism Unit of Santa Casa de Belo HorizonteProfessor of Medicine at University Center of Belo Horizonte – UNIBHBelo HorizonteBrazil
| | | | - Érico Higino de Carvalho
- Instituto de Medicina Integrada Professor Fernado Figueira, recifeFederal University of PernambucoRecifeBrazil
| | | | | | - Marcia Ribeiro
- Genetic Unit of Federal University of Rio de JaneiroRio de JaneiroBrazil
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9
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Grimbly C, Ludwig K, Wu Z, Caluseriu O, Rosolowsky E, Alexander RT, Ward LM, Rauch F. X-linked hypophosphatemia caused by a deep intronic variant in PHEX identified by PCR-based RNA analysis of urine-derived cells. Bone 2023; 176:116839. [PMID: 37454963 DOI: 10.1016/j.bone.2023.116839] [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: 05/03/2023] [Revised: 06/28/2023] [Accepted: 07/12/2023] [Indexed: 07/18/2023]
Abstract
X-linked hypophosphatemia (XLH) is caused by dominant inactivating mutations in the phosphate regulating endopeptidase homology, X-linked (PHEX), resulting in elevated fibroblast growth factor 23 (FGF23), hypophosphatemia, rickets and osteomalacia. PHEX variants are identified in approximately 85 % of individuals with XLH, which leaves a substantial proportion of patients with negative DNA-based genetic testing. Here we describe a 16-year-old male who had typical features of XLH on clinical and radiological examination. Genomic DNA sequencing of a hypophosphatemia gene panel did not reveal a pathogenic variant. We therefore obtained a urine sample, established cell cultures and obtained PHEX cDNA from urine-derived cells. Sequencing of exon-spanning PCR products demonstrated the presence of an 84 bp pseudoexon in PHEX intron 21 due to a deep intronic variant (c.2147+1197A>G), which created a new splice donor site in intron 21. The corresponding PHEX protein would lack 33 amino acids on the C-terminus and instead include an unrelated sequence of 17 amino acids. The patient and his affected mother both had this variant. This report highlights that individuals with the typical clinical characteristics of XLH and negative genomic DNA sequence analysis can have deep intronic PHEX variants that are detectable by PCR-based RNA diagnostics.
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Affiliation(s)
- Chelsey Grimbly
- Department of Pediatrics, University of Alberta, Edmonton, AB, Canada; Women and Children's Health Research Institute, Edmonton, AB, Canada.
| | - Karissa Ludwig
- Shriners Hospital for Children - Canada, Montreal, QC, Canada
| | - Zenghui Wu
- Shriners Hospital for Children - Canada, Montreal, QC, Canada
| | - Oana Caluseriu
- Women and Children's Health Research Institute, Edmonton, AB, Canada; Department of Genetics, University of Alberta, Edmonton, AB, Canada
| | - Elizabeth Rosolowsky
- Department of Pediatrics, University of Alberta, Edmonton, AB, Canada; Women and Children's Health Research Institute, Edmonton, AB, Canada
| | - R Todd Alexander
- Department of Pediatrics, University of Alberta, Edmonton, AB, Canada; Women and Children's Health Research Institute, Edmonton, AB, Canada
| | - Leanne M Ward
- Department of Pediatrics, University of Ottawa, Division of Endocrinology, Children's Hospital of Eastern Ontario, Ottawa, ON, Canada
| | - Frank Rauch
- Shriners Hospital for Children - Canada, Montreal, QC, Canada
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10
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Borghi M, da Silva LM, Bispo L, Longui CA. A genetic study of a Brazilian cohort of patients with X-linked hypophosphatemia reveals no correlation between genotype and phenotype. Front Pediatr 2023; 11:1215952. [PMID: 37794959 PMCID: PMC10546205 DOI: 10.3389/fped.2023.1215952] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/02/2023] [Accepted: 09/04/2023] [Indexed: 10/06/2023] Open
Abstract
Aim X-linked hypophosphatemia (XLH) is the most common inherited form of rickets, and it is caused by pathogenic inactivating variants of the phosphate-regulating endopeptidase homolog X-linked (PHEX) gene. The main purpose of this study is to identify the presence of a genotype-phenotype correlation in a cohort of XLH patients. Methods This is a retrospective study including patients diagnosed with hypophosphatemic rickets, confirmed by clinical, radiological, and laboratory findings. Medical records were reviewed for phenotypic analyses. Genomic DNA was extracted from the peripheral blood lymphocytes, and PHEX sequencing was performed by exomic NGS sequencing. The Wilcoxon rank-sum test and the two-tailed Fisher's exact test were employed for the statistical analyses of this study. Results A total of 41 patients were included in this study, and 63.41% (26/41) of the patients were female. The mutation analyses identified 29.27% missense variants and 29.72% nonsense variants, most of them were considered deleterious (66.41%). Six novel deleterious variants in the PHEX gene were detected in seven patients. The median concentrations of pretreatment serum calcium, phosphorus, and parathyroid hormone (PTH) were not significantly different among patients with different genotypes. An orthopedic surgery due to bone deformity was required in 57.69%. Conclusions Our analysis did not identify any specific genotype as a predictor. No significant genotype-phenotype correlation was found, suggesting that the recognition of subjacent pathogenic mutation in the PHEX gene may have limited prognostic value. Despite this finding, genetic testing may be useful for identifying affected individuals early and providing appropriate treatment.
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Affiliation(s)
- Mauro Borghi
- School of Medical Sciences Santa Casa SP and Pediatric Endocrinology Unit, Irmandade da Santa Casa de Misericórdia de São Paulo, São Paulo, Brazil
- Hospital São Luiz—Rede D´Or—CMA, Departament of Anesthesiology, São Paulo, Brazil
| | | | - Luciana Bispo
- Laboratório Mendelics, Department of Genetic, São Paulo, Brazil
| | - Carlos A. Longui
- School of Medical Sciences Santa Casa SP and Pediatric Endocrinology Unit, Irmandade da Santa Casa de Misericórdia de São Paulo, São Paulo, Brazil
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11
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Soto Barros J, Sanchez SI, Cabral K, Beggs AH, Agrawal PB, Genetti CA, Brownstein CA, Carpenter TO. X-linked hypophosphatemia in 4 generations due to an exon 13-15 duplication in PHEX, in the absence of the c.*231A>G variant. Bone 2023; 172:116763. [PMID: 37059315 PMCID: PMC10198939 DOI: 10.1016/j.bone.2023.116763] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Revised: 03/30/2023] [Accepted: 04/05/2023] [Indexed: 04/16/2023]
Abstract
X-linked hypophosphatemia is the most common cause of inherited rickets, due to inactivating variants of PHEX. More than 800 variants have been described to date and one which consists of a single base change in the 3' untranslated region (UTR) (c.*231A>G) is reported as prevalent in North America. Recently an exon 13-15 duplication has been found to occur in concert with the c.*231A>G variant, and thus it is unclear whether the pathogenicity is solely a function of the UTR variant. We present a family with XLH who harbors the exon 13-15 duplication but does not carry the 3'UTR variant, providing evidence that the duplication itself is the pathogenic variant when these two variants are found in cis.
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Affiliation(s)
- Julio Soto Barros
- Department of Pediatrics, Faculty of Medicine, University of Concepcion, Concepcion, Chile; Las Higueras Hospital, Talcahuano, Chile; Yale Center for X-Linked Hypophosphatemia, Department of Pediatrics (Endocrinology), Yale University, New Haven, CT 06519, United States of America
| | - Sabrina I Sanchez
- Manton Center for Orphan Disease Research, Division of Genetics and Genomics, Boston Children's Hospital, Boston, MA 02115, United States of America
| | - Kristin Cabral
- Manton Center for Orphan Disease Research, Division of Genetics and Genomics, Boston Children's Hospital, Boston, MA 02115, United States of America
| | - Alan H Beggs
- Manton Center for Orphan Disease Research, Division of Genetics and Genomics, Boston Children's Hospital, Boston, MA 02115, United States of America; Department of Pediatrics, Harvard Medical School, Boston, MA 02115, United States of America
| | - Pankaj B Agrawal
- Manton Center for Orphan Disease Research, Division of Genetics and Genomics, Boston Children's Hospital, Boston, MA 02115, United States of America; Department of Pediatrics, Harvard Medical School, Boston, MA 02115, United States of America; Division of Neonatology, Department of Pediatrics, University of Miami Miller School of Medicine and Holtz Children's Hospital, Jackson Health System, Miami, FL 33136, United States of America
| | - Casie A Genetti
- Manton Center for Orphan Disease Research, Division of Genetics and Genomics, Boston Children's Hospital, Boston, MA 02115, United States of America
| | - Catherine A Brownstein
- Manton Center for Orphan Disease Research, Division of Genetics and Genomics, Boston Children's Hospital, Boston, MA 02115, United States of America; Department of Pediatrics, Harvard Medical School, Boston, MA 02115, United States of America
| | - Thomas O Carpenter
- Yale Center for X-Linked Hypophosphatemia, Department of Pediatrics (Endocrinology), Yale University, New Haven, CT 06519, United States of America.
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12
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Insights into the Molecular and Hormonal Regulation of Complications of X-Linked Hypophosphatemia. ENDOCRINES 2023. [DOI: 10.3390/endocrines4010014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/06/2023] Open
Abstract
X-linked hypophosphatemia (XLH) is characterized by mutations in the PHEX gene, leading to elevated serum levels of FGF23, decreased production of 1,25 dihydroxyvitamin D3 (1,25D), and hypophosphatemia. Those affected with XLH manifest impaired growth and skeletal and dentoalveolar mineralization as well as increased mineralization of the tendon–bone attachment site (enthesopathy), all of which lead to decreased quality of life. Many molecular and murine studies have detailed the role of mineral ions and hormones in regulating complications of XLH, including how they modulate growth and growth plate maturation, bone mineralization and structure, osteocyte-mediated mineral matrix resorption and canalicular organization, and enthesopathy development. While these studies have provided insight into the molecular underpinnings of these skeletal processes, current therapies available for XLH do not fully prevent or treat these complications. Therefore, further investigations are needed to determine the molecular pathophysiology underlying the complications of XLH.
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13
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Abstract
Hypophosphatemic rickets typically presents in infancy or early childhood with skeletal deformities and growth plate abnormalities. The most common causes are genetic (such as X-linked hypophosphatemia), and these typically will result in lifelong hypophosphatemia and osteomalacia. Knowledge of phosphate metabolism, including the effects of fibroblast growth factor 23 (FGF23) (an osteocyte produced hormone that downregulates renal phosphate reabsorption and 1,25-dihydroxyvitamin-D (1,25(OH)2D) production), is critical to determining the underlying genetic or acquired causes of hypophosphatemia and to facilitate appropriate treatment. Serum phosphorus should be measured in any child or adult with musculoskeletal complaints suggesting rickets or osteomalacia. Clinical evaluation incudes thorough history, physical examination, laboratory investigations, genetic analysis (especially in the absence of a guiding family history), and imaging to establish etiology and to monitor severity and treatment course. The treatment depends on the underlying cause, but often includes active forms of vitamin D combined with phosphate salts, or anti-FGF23 antibody treatment (burosumab) for X-linked hypophosphatemia. The purpose of this article is to explore the approach to evaluating hypophosphatemic rickets and its treatment options.
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Affiliation(s)
- Sarah A Ackah
- Department of Medicine, Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Erik A Imel
- Department of Medicine, Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN 46202, USA
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14
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Abstract
Bone science has over the last decades unraveled many important pathways in bone and mineral metabolism and the interplay between genetic factors and the environment. Some of these discoveries have led to the development of pharmacological treatments of osteoporosis and rare bone diseases. Other scientific avenues have uncovered a role for the gut microbiome in regulating bone mass, which have led to investigations on the possible therapeutic role of probiotics in the prevention of osteoporosis. Huge advances have been made in identifying the genes that cause rare bone diseases, which in some cases have led to therapeutic interventions. Advances have also been made in understanding the genetic basis of the more common polygenic bone diseases, including osteoporosis and Paget's disease of bone (PDB). Polygenic profiles are used for establishing genetic risk scores aiming at early diagnosis and intervention, but also in Mendelian randomization (MR) studies to investigate both desired and undesired effects of targets for drug design.
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Affiliation(s)
- Bente L Langdahl
- Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus, Denmark; Institute of Clinical Medicine, Aarhus University, Aarhus, Denmark.
| | - André G Uitterlinden
- Laboratory for Population Genomics, Department of Internal Medicine, Erasmus MC, Rotterdam, the Netherlands
| | - Stuart H Ralston
- Centre for Genomic and Experimental Medicine, Institute of Genetics and Cancer, University of Edinburgh, Western General Hospital, Edinburgh EH4 2XU, UK
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15
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Pathogenic Variants of the PHEX Gene. ENDOCRINES 2022. [DOI: 10.3390/endocrines3030040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Twenty-five years ago, a pathogenic variant of the phosphate-regulating endopeptidase homolog X-linked (PHEX) gene was identified as the cause of X-linked hypophosphatemic rickets (XLH). Subsequently, the overproduction of fibroblast growth factor 23 (FGF23) due to PHEX defects has been found to be associated with XLH pathophysiology. However, the mechanism by which PHEX deficiency contributes to the upregulation of FGF23 and the function of PHEX itself remain unclear. To date, over 700 pathogenic variants have been identified in patients with XLH, and functional assays and genotype–phenotype correlation analyses based on pathogenic variant data derived from XLH patients have been reported. Genetic testing for XLH is useful for the diagnosis. Not only have single-nucleotide variants causing missense, nonsense, and splicing variants and small deletion/insertion variants causing frameshift/non-frameshift alterations been observed, but also gross deletion/duplication variants causing copy number variants have been reported as pathogenic variants in PHEX. With the development of new technologies including next generation sequencing, it is expected that an increasing number of pathogenic variants will be identified. This chapter aimed to summarize the genotype of PHEX and related analyses and discusses the pathophysiology of PHEX defects to seek clues on unsolved questions.
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16
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Jurca CM, Iuhas O, Kozma K, Petchesi CD, Zaha DC, Bembea M, Jurca S, Paul C, Jurca AD. Effects of Burosumab Treatment on Two Siblings with X-Linked Hypophosphatemia. Case Report and Literature Review. Genes (Basel) 2022; 13:genes13081392. [PMID: 36011303 PMCID: PMC9407333 DOI: 10.3390/genes13081392] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Revised: 08/01/2022] [Accepted: 08/03/2022] [Indexed: 11/16/2022] Open
Abstract
X-linked hypophosphatemia (XLH) or vitamin D-resistant rickets (MIM#307800), is a monogenic disorder with X-linked inheritance. It is caused by mutations present in the Phosphate Regulating Endopeptidase Homolog X-Linked (PHEX) gene responsible for the degradation of the bone-derived hormone fibroblast growth factor 23 (FGF23) into inactive fragments, but the entire mechanism is currently unclear. The inactivation of the gene prevents the degradation of FGF23, causing increased levels of FGF23, which leads to decreased tubular reabsorbtion of phosphorus. Clinical aspects are growth delay, limb deformities, bone pain, osteomalacia, dental anomalies, and enthesopathy. Laboratory evaluation shows hypophosphatemia, elevated alkaline phosphatase (ALP), and normal serum calcium levels, whereas parathormone (PTH) may be normal or increased and FGF23 greatly increased. Conventional treatment consists of administration of oral phosphate and calcitriol. Treatment with Burosumab, a monoclonal antibody that binds to FGF23, reducing its activity, was approved in 2018. Methods. We describe a case of two siblings, a girl and a boy, diagnosed with XLH, monitored by the Genetic Department of the County Emergency Clinical Hospital since 2019. The clinical picture is suggestive for XLH, both siblings exhibiting short stature, lower limb curvature, bone pain, marked walking weakness, and fatigue. Radiological aspects showed marked deformity of the lower limbs: genu varum in the girl, genu varum and valgum in the boy. Laboratory investigations showed hypophosphathemia, hyperphosphaturia, elevated ALP, normal PTH, and highly increased FGF23 in both. DNA analysis performed on the two siblings revealed a nonsense mutation in exone 5 of the PHEX gene: NM_000444.6(PHEX):c.565C > T (p.Gln189Ter). Results. At the age of 13½ on 7 June 2021, the two children started treatment with Burosumab in therapeutic doses and were monitored clinically and biochemically at regular intervals according to the protocol established by the Endocrinology Commission of the Romanian Health Ministry. Conclusions. The first results of the Burosumab treatment in the two siblings are extremely encouraging and suggest a favorable long-term evolution under this treatment.
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Affiliation(s)
- Claudia Maria Jurca
- Faculty of Medicine and Pharmacy, Department of Preclinical Disciplines, 1 December Sq., University of Oradea, 410081 Oradea, Romania
- Regional Center of Medical Genetics Bihor, County Emergency Clinical Hospital Oradea, Romania, (Part of ERN THACA), 410469 Oradea, Romania
| | - Oana Iuhas
- Regional Center of Medical Genetics Bihor, County Emergency Clinical Hospital Oradea, Romania, (Part of ERN THACA), 410469 Oradea, Romania
| | - Kinga Kozma
- Faculty of Medicine and Pharmacy, Department of Preclinical Disciplines, 1 December Sq., University of Oradea, 410081 Oradea, Romania
- Regional Center of Medical Genetics Bihor, County Emergency Clinical Hospital Oradea, Romania, (Part of ERN THACA), 410469 Oradea, Romania
| | - Codruta Diana Petchesi
- Faculty of Medicine and Pharmacy, Department of Preclinical Disciplines, 1 December Sq., University of Oradea, 410081 Oradea, Romania
- Correspondence:
| | - Dana Carmen Zaha
- Faculty of Medicine and Pharmacy, Department of Preclinical Disciplines, 1 December Sq., University of Oradea, 410081 Oradea, Romania
| | - Marius Bembea
- Faculty of Medicine and Pharmacy, Department of Preclinical Disciplines, 1 December Sq., University of Oradea, 410081 Oradea, Romania
| | - Sanziana Jurca
- Faculty of Medicine and Pharmacy, Department of Preclinical Disciplines, 1 December Sq., University of Oradea, 410081 Oradea, Romania
| | - Corina Paul
- Department of Pediatrics, Victor Babes University of Medicine and Pharmacy, 300041 Timisoara, Romania
| | - Alexandru Daniel Jurca
- Faculty of Medicine and Pharmacy, Department of Preclinical Disciplines, 1 December Sq., University of Oradea, 410081 Oradea, Romania
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Abstract
A number of genes that cause inherited kidney disorders reside on the X chromosome. Given that males have only a single active X chromosome, these disorders clinically manifest primarily in men and boys. However, phenotypes in female carriers of X-linked kidney conditions are becoming more and more recognized. This article reviews the biology of X inactivation as well as the kidney phenotype in women and girls with a number of X-linked kidney disorders including Alport syndrome, Fabry disease, nephrogenic diabetes insipidus, X-linked hypophosphatemic rickets, Dent disease, and Lowe syndrome.
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Affiliation(s)
- Catherine Quinlan
- Department of Nephrology, Royal Children's Hospital, Melbourne, Victoria, Australia; Department of Kidney Regeneration, Murdoch Children's Research Institute, Melbourne, Victoria, Australia; Department of Paediatrics, University of Melbourne, Melbourne, Victoria, Australia
| | - Michelle N Rheault
- Division of Pediatric Nephrology, Department of Pediatrics, University of Minnesota Masonic Children's Hospital, Minneapolis, MN.
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18
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Xu T, Tao X, Zhang Z, Yue H. Clinical and genetic characteristics of 29 Chinese patients with X-linked hypophosphatemia. Front Endocrinol (Lausanne) 2022; 13:956646. [PMID: 36060934 PMCID: PMC9437435 DOI: 10.3389/fendo.2022.956646] [Citation(s) in RCA: 0] [Impact Index Per Article: 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: 05/30/2022] [Accepted: 08/02/2022] [Indexed: 11/18/2022] Open
Abstract
OBJECTIVE The aim of this study was to fully describe the clinical and genetic characteristics, including clinical manifestations, intact fibroblast growth factor 23 (iFGF23) levels, and presence of PHEX gene mutations, of 22 and 7 patients with familial and sporadic X-linked dominant hypophosphatemia (XLH), respectively. METHODS Demographic data, clinical features, biochemical indicators, and imaging data of 29 patients were collected. All 22 exons and exon-intron boundaries of the PHEX gene were amplified by polymerase chain reaction (PCR) and directly sequenced. The serum level of iFGF23 was measured in 15 of the patients. RESULTS Twenty-nine patients (male/female: 13:16, juvenile/adult: 15:14) with XLH were included. The main symptoms were bowed lower extremities (89.7%), abnormal gait (89.7%), and short stature/growth retardation (78.6%). Hypophosphatemia with a high alkaline phosphatase level was the main biochemical feature and the median value of serum iFGF23 was 55.7 pg/ml (reference range: 16.1-42.2 pg/ml). Eight novel mutations in the PHEX gene were identified by Sanger sequencing, including two missense mutations (p. Gln682Leu and p. Phe312Ser), two deletions (c.350_356del and c.755_761del), one insertion (c.1985_1986insTGAC), and three splice mutations (c.1700+5G>C, c.1966-1G>T, and c.350-14_350-1del). Additionally, the recurrence rate after the first orthopedic surgery was 77.8% (7/9), and five of them had their first surgery before puberty. CONCLUSION Our study expanded the clinical phenotypes and gene mutation spectrum of XLH and provided a reference for the optimal timing of orthopedic surgeries.
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Affiliation(s)
| | | | | | - Hua Yue
- *Correspondence: Hua Yue, ; Zhenlin Zhang,
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