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Germeshausen M, Ballmaier M. CAMT-MPL: congenital amegakaryocytic thrombocytopenia caused by MPL mutations - heterogeneity of a monogenic disorder - a comprehensive analysis of 56 patients. Haematologica 2021; 106:2439-2448. [PMID: 32703794 PMCID: PMC8409039 DOI: 10.3324/haematol.2020.257972] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Indexed: 11/17/2022] Open
Abstract
Congenital amegakaryocytic thrombocytopenia caused by deleterious homozygous or compound heterozygous mutations in MPL (CAMT-MPL) is a rare inherited bone marrow failure syndrome presenting as an isolated thrombocytopenia at birth progressing to pancytopenia due to exhaustion of hematopoietic progenitors. The analysis of samples and clinical data from a large cohort of 56 patients with CAMT-MPL resulted in a detailed description of the clinical picture and reliable genotype-phenotype correlations for this rare disease. We extended the spectrum of CAMT causing MPL mutations regarding number (17 novel mutations) and impact. Clinical courses showed great variability with respect to the severity of thrombocytopenia, the development of pancytopenia and the consequences from bleedings. The most severe clinical problems were (i) intracranial bleedings pre- and perinatally and the resulting long-term consequences, and (ii) the development of aplastic anemia in the later course of the disease. An important and new finding was that thrombocytopenia was not detected at birth in a quarter of the patients. The rate of non-hematological abnormalities in CAMT-MPL was higher than described so far. Most of the anomalies were related to the head region (brain anomalies, ocular and orbital anomalies) and consequences of intracranial bleedings. The present study demonstrates a higher variability of clinical courses than described so far and has important implications on diagnosis and therapy. The diagnosis CAMT-MPL has to be considered even for those patients who are inconspicuous in the first months of life or show somatic anomalies typical for other inherited bone marrow failure syndromes.
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Affiliation(s)
- Manuela Germeshausen
- Central Research Facility Cell Sorting, Hannover Medical School, Hannover, Germany.
| | - Matthias Ballmaier
- Central Research Facility Cell Sorting, Hannover Medical School, Hannover, Germany.
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Congenital amegakaryocytic thrombocytopenia - Not a single disease. Best Pract Res Clin Haematol 2021; 34:101286. [PMID: 34404532 DOI: 10.1016/j.beha.2021.101286] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Revised: 07/09/2021] [Accepted: 07/12/2021] [Indexed: 01/05/2023]
Abstract
Congenital amegakaryocytic thrombocytopenia (CAMT) is a rare inherited bone marrow failure syndrome (IBMFS) that is characterized by severe thrombocytopenia at birth due to ineffective megakaryopoiesis and development towards aplastic anemia during the first years of life. CAMT is not a single monogenetic disorder; rather, many descriptions of CAMT include different entities with different etiologies. CAMT in a narrow sense, which is primarily restricted to the hematopoietic system, is caused mainly by mutations in the gene for the thrombopoietin receptor (MPL), sometimes in the gene for its ligand (THPO). CAMT in association with radio-ulnar synostosis, which is not always clinically apparent, is mostly caused by mutations in MECOM, rarely in HOXA11. Patients affected by other IBMFS - especially Fanconi anemia or dyskeratosis congenita - may be misdiagnosed as having CAMT when they lack typical disease features of these syndromes or have only mild symptoms. This article reviews scientific and clinical aspects of the various disorders associated with the term "CAMT" with a main focus on the disease caused by mutations in the MPL gene.
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Case Report: Clinical Variation in Children With Thrombopoietin Receptor (C-MPL) Mutations: Report of 2 Cases. J Pediatr Hematol Oncol 2018; 40:67-70. [PMID: 28859041 DOI: 10.1097/mph.0000000000000944] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Congenital amegakaryocytic thrombocytopenia (CAMT, MIM# 604498) is a rare congenital bone marrow failure syndrome which presents early in life with abnormal bleeding because of thrombocytopenia. Classically, megakaryocytes are decreased to absent in the bone marrow. The development of aplastic anemia early in childhood has led to the recommendation for early stem cell transplantation. Quantitative or loss-of-function mutations in the myeloproliferative leukemia gene (c-mpl), whose gene product functions as the thrombopoietin receptor, have been identified as causative for CAMT. Approximately 100 cases of CAMT are published in the medical literature. We describe 2 cases of CAMT who demonstrate disparate clinical courses, thereby highlighting phenotypic differences and increasing awareness of this clinical entity.
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Lorenz V, Ramsey H, Liu ZJ, Italiano J, Hoffmeister K, Bihorel S, Mager D, Hu Z, Slayton WB, Kile BT, Sola-Visner M, Ferrer-Marin F. Developmental Stage-Specific Manifestations of Absent TPO/c-MPL Signalling in Newborn Mice. Thromb Haemost 2017; 117:2322-2333. [PMID: 29212120 DOI: 10.1160/th17-06-0433] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Congenital amegakaryocytic thrombocytopaenia (CAMT) is a disorder caused by c-MPL mutations that impair thrombopoietin (TPO) signalling, resulting in a near absence of megakaryocytes (MKs). While this phenotype is consistent in adults, neonates with CAMT can present with severe thrombocytopaenia despite normal MK numbers. To investigate this, we characterized MKs and platelets in newborn c-MPL –/– mice. Liver MKs in c-MPL –/– neonates were reduced in number and size compared with wild-type (WT) age-matched MKs, and exhibited ultrastructural abnormalities not found in adult c-MPL –/– MKs. Platelet counts were lower in c-MPL –/– compared with WT mice at birth and did not increase over the first 2 weeks of life. In vivo biotinylation revealed a significant reduction in the platelet half-life of c-MPL –/– newborn mice (P2) compared with age-matched WT pups, which was not associated with ultrastructural abnormalities. Genetic deletion of the pro-apoptotic Bak did not rescue the severely reduced platelet half-life of c-MPL –/– newborn mice, suggesting that it was due to factors other than platelets entering apoptosis early. Indeed, adult GFP+ (green fluorescent protein transgenic) platelets transfused into thrombocytopenic c-MPL –/– P2 pups also had a shortened lifespan, indicating the importance of cell-extrinsic factors. In addition, neonatal platelets from WT and c-MPL –/– mice exhibited reduced P-selectin surface expression following stimulation compared with adult platelets of either genotype, and platelets from c-MPL –/– neonates exhibited reduced glycoprotein IIb/IIIa (GPIIb/IIIa) activation in response to thrombin compared with age-matched WT platelets. Taken together, our findings indicate that c-MPL deficiency is associated with abnormal maturation of neonatal MKs and developmental stage-specific defects in platelet function.
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Affiliation(s)
- Viola Lorenz
- Division of Newborn Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, United States
| | - Haley Ramsey
- Division of Newborn Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, United States
| | - Zhi-Jian Liu
- Division of Newborn Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, United States
| | - Joseph Italiano
- Division of Hematology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, United States
| | - Karin Hoffmeister
- Division of Hematology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, United States.,Blood Center of Wisconsin, Blood Research Institute, Milwaukee, Wisconsin, United States
| | - Sihem Bihorel
- Department of Pharmaceutical Sciences, University of Buffalo, State University of New York, Buffalo, New York, United States.,College of Pharmacy, Center for Pharmacometrics and Systems Pharmacology, Orlando, Florida, United States
| | - Donald Mager
- Department of Pharmaceutical Sciences, University of Buffalo, State University of New York, Buffalo, New York, United States
| | - Zhongbo Hu
- Department of Pediatrics, University of Florida, Gainesville, Florida, United States
| | - William B Slayton
- Department of Pediatrics, University of Florida, Gainesville, Florida, United States
| | - Benjamin T Kile
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia.,Department of Anatomy and Developmental Biology, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Australia
| | - Martha Sola-Visner
- Division of Newborn Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, United States
| | - Francisca Ferrer-Marin
- Division of Newborn Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, United States.,Unidad de Hematología y Oncología Médica, Hospital Morales-Meseguer, Centro de Hemodonacion, IMIB-Murcia, CIBERER (CB15/00055), UCAM, Spain
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Ok Bozkaya İ, Yaralı N, Işık P, Ünsal Saç R, Tavil B, Tunç B. Severe Clinical Course in a Patient with Congenital Amegakaryocytic Thrombocytopenia Due to a Missense Mutation of the c-MPL Gene. Turk J Haematol 2017; 32:172-4. [PMID: 26316487 PMCID: PMC4451487 DOI: 10.4274/tjh.2013.0191] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
Congenital amegakaryocytic thrombocytopenia (CAMT) generally begins at birth with severe thrombocytopenia and progresses to pancytopenia. It is caused by mutations in the thrombopoietin receptor gene, the myeloproliferative leukemia virus oncogene (c-MPL). The association between CAMT and c-MPL mutation type has been reported in the literature. Patients with CAMT have been categorized according to their clinical symptoms caused by different mutations. Missense mutations of c-MPL have been classified as type II and these patients have delayed onset of bone marrow failure compared to type I patients. Here we present a girl with severe clinical course of CAMT II having a missense mutation in exon 4 of the c-MPL gene who was admitted to our hospital with intracranial hemorrhage during the newborn period.
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Affiliation(s)
- İkbal Ok Bozkaya
- Ankara Children's Hematology Oncology Hospital, Clinic of Pediatric Hematology, Ankara, Turkey Phone: +90 312 396 99 70 E-mail:
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Abstract
PURPOSE OF REVIEW The inherited platelet disorders have witnessed a surge in our understanding of molecular mechanisms of disease in the past few years due in large to part to the introduction of next-generation sequencing for discovery of novel genes. The purpose of this review is to update the reader on the novel discoveries with regard to the inherited platelet disorders, with a particular focus on describing the novel disorders described most recently. RECENT FINDINGS The description of novel mechanisms of disease including mutations in PRKACG, in a family with severe macrothrombocytopenia, RUNX1 and FLI1 mutations in patients with inherited mild platelet function disorders and CalDAG-GEFI resulting in a severe platelet bleeding phenotype show that there is still much to be learned from studying families and molecular sequencing of patients with well phenotyped platelet disorders. SUMMARY The implications for clinical practice of the continually growing list of genes described in small numbers of families makes whole exome/genome tempting as an option for evaluation of patients, but use outside of the research setting still needs to be done with extreme caution as interpretation of variants is likely to require additional studies.
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Cardona I, Ferretti E, Daboval T, Klaassen RJ, Dror Y. Case 1: A newborn with pancytopenia. Paediatr Child Health 2016; 21:9-11. [PMID: 26941551 DOI: 10.1093/pch/21.1.9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- Isabel Cardona
- Department of Otolaryngology Pediatrics - Head & Neck Surgery, McGill University Health Centre, Montreal Children's Hospital, Montreal, Quebec
| | | | | | - Robert J Klaassen
- Department of Pediatrics, Division of Oncology and Hematology, Children's Hospital of Eastern Ontario, Ottawa, Ontario
| | - Yigal Dror
- Department of Pediatrics, Division of Hematology Oncology, Marrow Failure and Myelodysplasia Program, The Hospital for Sick Children, Toronto, Ontario
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Mahadeo KM, Tewari P, Parikh SH, Driscoll TA, Page K, Martin PL, Kurtzberg J, Prasad VK. Durable engraftment and correction of hematological abnormalities in children with congenital amegakaryocytic thrombocytopenia following myeloablative umbilical cord blood transplantation. Pediatr Transplant 2015; 19:753-7. [PMID: 26369627 DOI: 10.1111/petr.12577] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 07/10/2015] [Indexed: 11/26/2022]
Abstract
The use of HSCT is the only potentially curative treatment for CAMT, but access is limited by the availability of suitable donors. We report five consecutive patients with CAMT who received MAC and partially HLA-mismatched, UCBT (unrelated, n = 4). Median times to neutrophil (>500/μL) and platelet (≥20 000 and ≥50 000/μL) engraftment were 19, 57, and 70 days, respectively. Acute GvHD, grade II, developed in one patient, who subsequently developed limited chronic GvHD. At median follow-up of 14 yr, all patients are alive with sustained donor cell engraftment. To our knowledge, this is the largest single-center series of UCBT for patients with this disease and suggests that UCBT is a successful curative option for patients with CAMT.
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Affiliation(s)
- Kris M Mahadeo
- Blood and Marrow and Transplantation Program, Department of Pediatrics, Duke University Medical Center, Durham, NC, USA
| | - Priti Tewari
- Blood and Marrow and Transplantation Program, Department of Pediatrics, Duke University Medical Center, Durham, NC, USA
| | - Suhag H Parikh
- Blood and Marrow and Transplantation Program, Department of Pediatrics, Duke University Medical Center, Durham, NC, USA
| | - Timothy A Driscoll
- Blood and Marrow and Transplantation Program, Department of Pediatrics, Duke University Medical Center, Durham, NC, USA
| | - Kristin Page
- Blood and Marrow and Transplantation Program, Department of Pediatrics, Duke University Medical Center, Durham, NC, USA
| | - Paul L Martin
- Blood and Marrow and Transplantation Program, Department of Pediatrics, Duke University Medical Center, Durham, NC, USA
| | - Joanne Kurtzberg
- Blood and Marrow and Transplantation Program, Department of Pediatrics, Duke University Medical Center, Durham, NC, USA
| | - Vinod K Prasad
- Blood and Marrow and Transplantation Program, Department of Pediatrics, Duke University Medical Center, Durham, NC, USA
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Woods G, Bajwa RPS, Rose MJ. Reduced intensity transplantation for congenital amegakaryocytic thrombocytopenia: report of a case and review of the literature. Pediatr Transplant 2014; 18:E31-4. [PMID: 24119002 DOI: 10.1111/petr.12175] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 08/29/2013] [Indexed: 11/28/2022]
Abstract
CAMT is a bone marrow failure syndrome that usually presents with isolated thrombocytopenia soon after birth. HSCT is curative, and MAC is associated with increased transplant-related morbidity and mortality, especially in the unrelated setting. We used a RIC regimen with alemtuzumab, fludarabine, and melphalan in a seven-month-old patient with CAMT who underwent a MUD HSCT. The transplant was well tolerated with few complications. Neutrophil and platelet engraftment occurred on day +12 and +29, respectively, and she had 100% donor chimerisms on days +19.
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Affiliation(s)
- Gary Woods
- Department of Hematology/Oncology/BMT, Nationwide Children's Hospital, Ohio State University, Columbus, OH, USA
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Varghese LN, Zhang JG, Young SN, Willson TA, Alexander WS, Nicola NA, Babon JJ, Murphy JM. Functional characterization of c-Mpl ectodomain mutations that underlie congenital amegakaryocytic thrombocytopenia. Growth Factors 2014; 32:18-26. [PMID: 24438083 DOI: 10.3109/08977194.2013.874347] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Activation of the cell surface receptor, c-Mpl, by the cytokine, thrombopoietin (TPO), underpins megakaryocyte and platelet production in mammals. In humans, mutations in c-Mpl have been identified as the molecular basis of Congenital Amegakaryocytic Thrombocytopenia (CAMT). Here, we show that CAMT-associated mutations in c-Mpl principally lead to defective receptor presentation on the cell surface. In contrast, one CAMT mutant c-Mpl, F104S, was expressed on the cell surface, but showed defective TPO binding and receptor activation. Using mutational analyses, we examined which residues adjacent to F104 within the membrane-distal cytokine receptor homology module (CRM) of c-Mpl comprise the TPO-binding epitope, revealing residues within the predicted Domain 1 E-F and A-B loops and Domain 2 F'-G' loop as key TPO-binding determinants. These studies underscore the importance of the c-Mpl membrane-distal CRM to TPO-binding and suggest that mutations within this CRM that perturb TPO binding could give rise to CAMT.
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Affiliation(s)
- Leila N Varghese
- The Walter and Eliza Hall Institute of Medical Research , Parkville, Victoria , Australia and
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Abstract
Molecular pathogenesis may be elucidated for inherited bone marrow failure syndromes (IBMFS). The study and presentation of the details of their molecular biology and biochemistry is warranted for appropriate diagnosis and management of afflicted patients and to identify the physiology of the normal hematopoiesis and mechanisms of carcinogenesis. Several themes have emerged within each subsection of IBMFS, including the ribosomopathies, which include ribosome assembly and ribosomal RNA processing. The Fanconi anemia pathway has become interdigitated with the familial breast cancer syndromes. In this article, the diseases that account for most IBMFS diagnoses are analyzed.
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Affiliation(s)
- S Deborah Chirnomas
- Section of Pediatric Hematology-Oncology, LMP 2073, Yale School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
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