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Ramdas S, Beeson D, Dong YY. Congenital myasthenic syndromes: increasingly complex. Curr Opin Neurol 2024; 37:493-501. [PMID: 39051439 PMCID: PMC11377046 DOI: 10.1097/wco.0000000000001300] [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: 07/27/2024]
Abstract
PURPOSE OF REVIEW Congenital myasthenia syndromes (CMS) are treatable, inherited disorders affecting neuromuscular transmission. We highlight that the involvement of an increasing number of proteins is making the understanding of the disease mechanisms and potential treatments progressively more complex. RECENT FINDINGS Although early studies identified mutations of proteins directly involved in synaptic transmission at the neuromuscular junction, recently, next-generation sequencing has facilitated the identification of many novel mutations in genes that encode proteins that have a far wider expression profile, some even ubiquitously expressed, but whose defective function leads to impaired neuromuscular transmission. Unsurprisingly, mutations in these genes often causes a wider phenotypic disease spectrum where defective neuromuscular transmission forms only one component. This has implications for the management of CMS patients. SUMMARY Given the widening nonneuromuscular junction phenotypes in the newly identified forms of CMS, new therapies need to include disease-modifying approaches that address not only neuromuscular weakness but also the multisystem involvement. Whilst the current treatments for CMS are highly effective for many subtypes there remains, in a proportion of CMS patients, an unmet need for more efficacious therapies.
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Affiliation(s)
- Sithara Ramdas
- MDUK Neuromuscular Centre, Department of Paediatrics, University of Oxford
- Department of Paediatric Neurology, John Radcliffe Hospital
| | - David Beeson
- Neurosciences Group, Weatherall Institute of Molecular Medicine, The John Radcliffe, Oxford OX3 9DS
| | - Yin Yao Dong
- Neurosciences Group, Weatherall Institute of Molecular Medicine, The John Radcliffe, Oxford OX3 9DS
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Tan KA, Chew HB, Yacob Y, Khoo TB. A Common CHAT Gene Mutation of Congenital Myasthenic Syndrome Found in Kadazandusun Children. J Pediatr Genet 2024; 13:232-236. [PMID: 39086444 PMCID: PMC11288710 DOI: 10.1055/s-0042-1750747] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2021] [Accepted: 03/09/2022] [Indexed: 10/14/2022]
Abstract
Congenital myasthenic syndrome (CMS) is an uncommon inherited neuromuscular junction disease. The clinical presentation of this disorder is diverse. Typically patients with this disorder present with early-onset swallowing difficulty and apnea in infancy, fluctuating ocular palsies and fatigable proximal muscle weakness during childhood, and late-onset form involving progressive weakness in adulthood. Difficulty in performing neurophysiology studies in children and the absence of a pathognomonic investigation marker increase the challenges in diagnosis of this disorder. The emergence of next-generation sequencing technology has circumvented these challenges somewhat, and has contributed to the discovery of novel mutations. We present here diagnostic odyssey of three CMS patients from two unrelated Kadazandusun kinships and their follow-up treatment. A rare homozygous mutation c.916G > C (p.Val306Leu) in CHAT gene was found in two siblings born of a consanguineous marriage. Third patient had compound heterozygous mutations c.406G > A (p.Val136Met) and c.916G > C (p.Val306Leu) in CHAT gene. We postulate that p.Val306Leu may be a founder mutation in the Kadazandusuns, an indigenous ethnic minority of Borneo Island.
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Affiliation(s)
- Khian Aun Tan
- Pediatric Neurology Unit, Hospital Tunku Azizah, Kuala Lumpur, Malaysia.
| | - Hui Bein Chew
- Genetic Department, Hospital Kuala Lumpur, Kuala Lumpur, Malaysia
| | - Yusnita Yacob
- Molecular Diagnostics Unit, Institute for Medical Research, National Institutes of Health, Selangor, Malaysia
| | - Teik Beng Khoo
- Pediatric Neurology Unit, Hospital Tunku Azizah, Kuala Lumpur, Malaysia.
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Spendiff S, Dong Y, Maggi L, Rodríguez Cruz PM, Beeson D, Lochmüller H. 260th ENMC International Workshop: Congenital myasthenic syndromes 11-13 March 2022, Hoofddorp, The Netherlands. Neuromuscul Disord 2023; 33:111-118. [PMID: 36609117 DOI: 10.1016/j.nmd.2022.12.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Revised: 12/02/2022] [Accepted: 12/13/2022] [Indexed: 12/23/2022]
Affiliation(s)
- Sally Spendiff
- Children's Hospital of Eastern Ontario Research Institute, Ottawa, Canada
| | - Yin Dong
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
| | - Lorenzo Maggi
- Neuroimmunology and Neuromuscular Diseases Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Pedro M Rodríguez Cruz
- Centro Nacional de Análisis Genómico (CNAG-CRG), Centre for Genomic Regulation, Barcelona, Spain; Department of Human Genetics, Université Cheikh Anta Diop, Dakar, Senegal; Department of Neuromuscular Diseases, UCL Institute of Neurology, London, UK
| | - David Beeson
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
| | - Hanns Lochmüller
- Children's Hospital of Eastern Ontario Research Institute, Ottawa, Canada; Department of Medicine, Division of Neurology, The Ottawa Hospital, Ottawa, Canada; Brain and Mind Research Institute, University of Ottawa, Ottawa, Canada; Department of Neuropediatrics and Muscle Disorders, Medical Center - University of Freiburg, Faculty of Medicine, Freiburg, Germany; Centro Nacional de Análisis Genómico (CNAG-CRG), Center for Genomic Regulation, Barcelona Institute of Science and Technology (BIST), Barcelona, Catalonia, Spain.
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Ohno K, Ohkawara B, Shen XM, Selcen D, Engel AG. Clinical and Pathologic Features of Congenital Myasthenic Syndromes Caused by 35 Genes-A Comprehensive Review. Int J Mol Sci 2023; 24:ijms24043730. [PMID: 36835142 PMCID: PMC9961056 DOI: 10.3390/ijms24043730] [Citation(s) in RCA: 36] [Impact Index Per Article: 36.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2023] [Revised: 02/09/2023] [Accepted: 02/09/2023] [Indexed: 02/16/2023] Open
Abstract
Congenital myasthenic syndromes (CMS) are a heterogeneous group of disorders characterized by impaired neuromuscular signal transmission due to germline pathogenic variants in genes expressed at the neuromuscular junction (NMJ). A total of 35 genes have been reported in CMS (AGRN, ALG14, ALG2, CHAT, CHD8, CHRNA1, CHRNB1, CHRND, CHRNE, CHRNG, COL13A1, COLQ, DOK7, DPAGT1, GFPT1, GMPPB, LAMA5, LAMB2, LRP4, MUSK, MYO9A, PLEC, PREPL, PURA, RAPSN, RPH3A, SCN4A, SLC18A3, SLC25A1, SLC5A7, SNAP25, SYT2, TOR1AIP1, UNC13A, VAMP1). The 35 genes can be classified into 14 groups according to the pathomechanical, clinical, and therapeutic features of CMS patients. Measurement of compound muscle action potentials elicited by repetitive nerve stimulation is required to diagnose CMS. Clinical and electrophysiological features are not sufficient to identify a defective molecule, and genetic studies are always required for accurate diagnosis. From a pharmacological point of view, cholinesterase inhibitors are effective in most groups of CMS, but are contraindicated in some groups of CMS. Similarly, ephedrine, salbutamol (albuterol), amifampridine are effective in most but not all groups of CMS. This review extensively covers pathomechanical and clinical features of CMS by citing 442 relevant articles.
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Affiliation(s)
- Kinji Ohno
- Division of Neurogenetics, Center for Neurological Diseases and Cancer, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan
- Correspondence: (K.O.); (A.G.E.)
| | - Bisei Ohkawara
- Division of Neurogenetics, Center for Neurological Diseases and Cancer, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan
| | - Xin-Ming Shen
- Department of Neurology and Neuromuscular Research Laboratory, Mayo Clinic, Rochester, MN 55905, USA
| | - Duygu Selcen
- Department of Neurology and Neuromuscular Research Laboratory, Mayo Clinic, Rochester, MN 55905, USA
| | - Andrew G. Engel
- Department of Neurology and Neuromuscular Research Laboratory, Mayo Clinic, Rochester, MN 55905, USA
- Correspondence: (K.O.); (A.G.E.)
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Stojkovic T, Masingue M, Turmel H, Hezode-Arzel M, Béhin A, Leonard-Louis S, Bassez G, Bauché S, Blondy P, Richard P, Sternberg D, Eymard B, Fournier E, Villar-Quiles RN. Diagnostic yield of a practical electrodiagnostic protocol discriminating between different congenital myasthenic syndromes. Neuromuscul Disord 2022; 32:870-878. [PMID: 36522822 DOI: 10.1016/j.nmd.2022.10.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Revised: 09/28/2022] [Accepted: 10/02/2022] [Indexed: 11/07/2022]
Abstract
Congenital myasthenic syndromes (CMS) are a group of heterogeneous diseases of the neuromuscular junction. We report electrodiagnostic testing (EDX) and genetic findings in a series of 120 CMS patients tested with a simple non-invasive EDX workup with surface recording of CMAPs and 3Hz repetitive nerve stimulation of accessory, radial and deep fibular nerves. Five ENMG phenotypes were retrieved based on the presence or not of R-CMAPs and the distribution pattern of decremental CMAP responses which significantly correlated with genetic findings (p <0.00001). R-CMAPs were found in all COLQ-mutated patients (CMS1A) and Slow Channel CMS (SCCMS) (CMS1B). CMS1A exhibited greater decrements in accessory nerve RNS than CMS1B. Patients without R-CMAPs were classified into CMS2A (DOK7-, MUSK-, GFPT1-, GMPPB-, TOR1AIP-mutated) when exhibiting predominant accessory nerve RNS decrements, CMS2B (CHRNE, CHRND, RAPSN) with predominant radial nerve RNS decrements, or CMS2C (AGRN) if there were predominant fibular decrements. Our algorithm may have a major impact on diagnostic and therapeutic monitoring in CMS patients, as well as for validation of the pathogenicity of genetic variants. It should also be part of the evaluation of unexplained muscle weakness or complex neuromuscular phenotypes.
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Affiliation(s)
- Tanya Stojkovic
- Reference Center for Neuromuscular Disorders (Nord/Est/Ile de France), Institute of Myology, Pitié-Salpêtrière Hospital, APHP, Pitié-Salpêtrière Hospital, Paris, France; Centre de Recherche en Myologie, Sorbonne Université-Inserm UMRS974, Paris, France
| | - Marion Masingue
- Reference Center for Neuromuscular Disorders (Nord/Est/Ile de France), Institute of Myology, Pitié-Salpêtrière Hospital, APHP, Pitié-Salpêtrière Hospital, Paris, France
| | - Helène Turmel
- Department of Neurophysiology, APHP, Pitié Salpetrière hospital, Paris, France
| | | | - Anthony Béhin
- Reference Center for Neuromuscular Disorders (Nord/Est/Ile de France), Institute of Myology, Pitié-Salpêtrière Hospital, APHP, Pitié-Salpêtrière Hospital, Paris, France
| | - Sarah Leonard-Louis
- Reference Center for Neuromuscular Disorders (Nord/Est/Ile de France), Institute of Myology, Pitié-Salpêtrière Hospital, APHP, Pitié-Salpêtrière Hospital, Paris, France
| | - Guillaume Bassez
- Reference Center for Neuromuscular Disorders (Nord/Est/Ile de France), Institute of Myology, Pitié-Salpêtrière Hospital, APHP, Pitié-Salpêtrière Hospital, Paris, France; Centre de Recherche en Myologie, Sorbonne Université-Inserm UMRS974, Paris, France
| | - Stéphanie Bauché
- Centre de Recherche en Myologie, Sorbonne Université-Inserm UMRS974, Paris, France
| | - Patricia Blondy
- National Reference Center for Muscle Channelopathies, APHP, Pitié Salpetrière hospital, Paris, France; Biochemistry Department, Center of Molecular and Cellular Genetics, APHP, Pitié Salpetrière hospital, Paris, France
| | - Pascale Richard
- Biochemistry Department, Center of Molecular and Cellular Genetics, APHP, Pitié Salpetrière hospital, Paris, France
| | - Damien Sternberg
- National Reference Center for Muscle Channelopathies, APHP, Pitié Salpetrière hospital, Paris, France; Biochemistry Department, Center of Molecular and Cellular Genetics, APHP, Pitié Salpetrière hospital, Paris, France
| | - Bruno Eymard
- Reference Center for Neuromuscular Disorders (Nord/Est/Ile de France), Institute of Myology, Pitié-Salpêtrière Hospital, APHP, Pitié-Salpêtrière Hospital, Paris, France
| | - Emmanuel Fournier
- Department of Neurophysiology, APHP, Pitié Salpetrière hospital, Paris, France; National Reference Center for Muscle Channelopathies, APHP, Pitié Salpetrière hospital, Paris, France; Department of Physiology, Sorbonne University, Faculté de médecine Pitié-Salpêtrière, Paris, France
| | - Rocío Nur Villar-Quiles
- Reference Center for Neuromuscular Disorders (Nord/Est/Ile de France), Institute of Myology, Pitié-Salpêtrière Hospital, APHP, Pitié-Salpêtrière Hospital, Paris, France; Centre de Recherche en Myologie, Sorbonne Université-Inserm UMRS974, Paris, France
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LRP4-IgG service line testing in seronegative myasthenia gravis and controls. J Neuroimmunol 2022; 368:577895. [DOI: 10.1016/j.jneuroim.2022.577895] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Revised: 04/25/2022] [Accepted: 05/14/2022] [Indexed: 11/13/2022]
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Della Marina A, Arlt A, Schara-Schmidt U, Depienne C, Gangfuß A, Kölbel H, Sickmann A, Freier E, Kohlschmidt N, Hentschel A, Weis J, Czech A, Grüneboom A, Roos A. Phenotypical and Myopathological Consequences of Compound Heterozygous Missense and Nonsense Variants in SLC18A3. Cells 2021; 10:cells10123481. [PMID: 34943989 PMCID: PMC8700530 DOI: 10.3390/cells10123481] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2021] [Revised: 11/11/2021] [Accepted: 11/12/2021] [Indexed: 11/16/2022] Open
Abstract
Background: Presynaptic forms of congenital myasthenic syndromes (CMS) due to pathogenic variants in SLC18A3 impairing the synthesis and recycling of acetylcholine (ACh) have recently been described. SLC18A3 encodes the vesicular ACh transporter (VAChT), modulating the active transport of ACh at the neuromuscular junction, and homozygous loss of VAChT leads to lethality. Methods: Exome sequencing (ES) was carried out to identify the molecular genetic cause of the disease in a 5-year-old male patient and histological, immunofluorescence as well as electron- and CARS-microscopic studies were performed to delineate the muscle pathology, which has so far only been studied in VAChT-deficient animal models. Results: ES unraveled compound heterozygous missense and nonsense variants (c.315G>A, p.Trp105* and c.1192G>C, p.Asp398His) in SLC18A3. Comparison with already-published cases suggests a more severe phenotype including impaired motor and cognitive development, possibly related to a more severe effect of the nonsense variant. Therapy with pyridostigmine was only partially effective while 3,4 diaminopyridine showed no effect. Microscopic investigation of the muscle biopsy revealed reduced fibre size and a significant accumulation of lipid droplets. Conclusions: We suggest that nonsense variants have a more detrimental impact on the clinical manifestation of SLC18A3-associated CMS. The impact of pathogenic SLC18A3 variants on muscle fibre integrity beyond the effect of denervation is suggested by the build-up of lipid aggregates. This in turn implicates the importance of proper VAChT-mediated synthesis and recycling of ACh for lipid homeostasis in muscle cells. This hypothesis is further supported by the pathological observations obtained in previously published VAChT-animal models.
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Affiliation(s)
- Adela Della Marina
- Department of Pediatric Neurology, Centre for Neuromuscular Disorders, Centre for Translational Neuro- and Behavioral Sciences, University Duisburg-Essen, 45122 Essen, Germany; (U.S.-S.); (A.G.); (H.K.); (A.R.)
- Correspondence:
| | - Annabelle Arlt
- Institute of Clinical Genetics and Tumor Genetics Bonn, 53111 Bonn, Germany; (A.A.); (N.K.)
| | - Ulrike Schara-Schmidt
- Department of Pediatric Neurology, Centre for Neuromuscular Disorders, Centre for Translational Neuro- and Behavioral Sciences, University Duisburg-Essen, 45122 Essen, Germany; (U.S.-S.); (A.G.); (H.K.); (A.R.)
| | - Christel Depienne
- Institute of Human Genetics, University Hospital Essen, University of Duisburg-Essen, 45122 Essen, Germany;
| | - Andrea Gangfuß
- Department of Pediatric Neurology, Centre for Neuromuscular Disorders, Centre for Translational Neuro- and Behavioral Sciences, University Duisburg-Essen, 45122 Essen, Germany; (U.S.-S.); (A.G.); (H.K.); (A.R.)
| | - Heike Kölbel
- Department of Pediatric Neurology, Centre for Neuromuscular Disorders, Centre for Translational Neuro- and Behavioral Sciences, University Duisburg-Essen, 45122 Essen, Germany; (U.S.-S.); (A.G.); (H.K.); (A.R.)
| | - Albert Sickmann
- Leibniz-Institut für Analytische Wissenschaften -ISAS- e.V., 44139 Dortmund, Germany; (A.S.); (E.F.); (A.H.); (A.C.); (A.G.)
| | - Erik Freier
- Leibniz-Institut für Analytische Wissenschaften -ISAS- e.V., 44139 Dortmund, Germany; (A.S.); (E.F.); (A.H.); (A.C.); (A.G.)
| | - Nicolai Kohlschmidt
- Institute of Clinical Genetics and Tumor Genetics Bonn, 53111 Bonn, Germany; (A.A.); (N.K.)
| | - Andreas Hentschel
- Leibniz-Institut für Analytische Wissenschaften -ISAS- e.V., 44139 Dortmund, Germany; (A.S.); (E.F.); (A.H.); (A.C.); (A.G.)
| | - Joachim Weis
- Institute of Neuropathology, University Hospital Aachen, RWTH-Aachen University, 52074 Aachen, Germany;
| | - Artur Czech
- Leibniz-Institut für Analytische Wissenschaften -ISAS- e.V., 44139 Dortmund, Germany; (A.S.); (E.F.); (A.H.); (A.C.); (A.G.)
| | - Anika Grüneboom
- Leibniz-Institut für Analytische Wissenschaften -ISAS- e.V., 44139 Dortmund, Germany; (A.S.); (E.F.); (A.H.); (A.C.); (A.G.)
| | - Andreas Roos
- Department of Pediatric Neurology, Centre for Neuromuscular Disorders, Centre for Translational Neuro- and Behavioral Sciences, University Duisburg-Essen, 45122 Essen, Germany; (U.S.-S.); (A.G.); (H.K.); (A.R.)
- Children’s Hospital of Eastern Ontario Research Institute, Ottawa, ON K1H 8L1, Canada
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Nicolau S, Milone M, Liewluck T. Guidelines for genetic testing of muscle and neuromuscular junction disorders. Muscle Nerve 2021; 64:255-269. [PMID: 34133031 DOI: 10.1002/mus.27337] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Accepted: 05/28/2021] [Indexed: 12/24/2022]
Abstract
Despite recent advances in the understanding of inherited muscle and neuromuscular junction diseases, as well as the advent of a wide range of genetic tests, patients continue to face delays in diagnosis of sometimes treatable disorders. These guidelines outline an approach to genetic testing in such disorders. Initially, a patient's phenotype is evaluated to identify myopathies requiring directed testing, including myotonic dystrophies, facioscapulohumeral muscular dystrophy, oculopharyngeal muscular dystrophy, mitochondrial myopathies, dystrophinopathies, and oculopharyngodistal myopathy. Initial investigation in the remaining patients is generally a comprehensive gene panel by next-generation sequencing. Broad panels have a higher diagnostic yield and can be cost-effective. Due to extensive phenotypic overlap and treatment implications, genes responsible for congenital myasthenic syndromes should be included when evaluating myopathy patients. For patients whose initial genetic testing is negative or inconclusive, phenotypic re-evaluation is warranted, along with consideration of genes and variants not included initially, as well as their acquired mimickers.
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Affiliation(s)
- Stefan Nicolau
- Department of Neurology, Mayo Clinic, Rochester, Minnesota, USA
| | | | - Teerin Liewluck
- Department of Neurology, Mayo Clinic, Rochester, Minnesota, USA
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The congenital myasthenic syndromes: expanding genetic and phenotypic spectrums and refining treatment strategies. Curr Opin Neurol 2020; 32:696-703. [PMID: 31361628 PMCID: PMC6735524 DOI: 10.1097/wco.0000000000000736] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Congenital myasthenic syndromes (CMS) are a group of heterogeneous inherited disorders caused by mutations in genes encoding proteins whose function is essential for the integrity of neuromuscular transmission. This review updates the reader on the expanding phenotypic spectrum and suggested improved treatment strategies.
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Al-Futaisi A, Ahmad F, Al-Kasbi G, Al-Thihli K, Koul R, Al-Maawali A. Missense mutations in SLC25A1 are associated with congenital myasthenic syndrome type 23. Clin Genet 2019; 97:666-667. [PMID: 31808147 DOI: 10.1111/cge.13678] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2019] [Revised: 11/14/2019] [Accepted: 11/18/2019] [Indexed: 01/19/2023]
Affiliation(s)
- Amna Al-Futaisi
- Department of Child Health, College of Medicine and Health Sciences, Sultan Qaboos University, Muscat, Oman
| | - Faraz Ahmad
- Department of Child Health, College of Medicine and Health Sciences, Sultan Qaboos University, Muscat, Oman
| | - Ghalia Al-Kasbi
- Department of Genetics, College of Medicine and Health Sciences, Sultan Qaboos University, Muscat, Oman
| | - Khalid Al-Thihli
- Department of Genetics, College of Medicine and Health Sciences, Sultan Qaboos University, Muscat, Oman.,Genetic and Developmental Medicine Clinic, Sultan Qaboos University Hospital, Muscat, Oman
| | - Roshan Koul
- Department of Child Health, College of Medicine and Health Sciences, Sultan Qaboos University, Muscat, Oman
| | - Almundher Al-Maawali
- Department of Genetics, College of Medicine and Health Sciences, Sultan Qaboos University, Muscat, Oman.,Genetic and Developmental Medicine Clinic, Sultan Qaboos University Hospital, Muscat, Oman
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