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London, United Kingdom

Cullup T.,DNA Laboratory | Lamont P.J.,Neurogenetics Unit | Cirak S.,University College London | Damian M.S.,Royal Infirmary | And 11 more authors.
Neuromuscular Disorders

Central Core Disease (CCD) and Multi-minicore Disease (MmD) (the "core myopathies") have been mainly associated with mutations in the skeletal muscle ryanodine receptor (RYR1) and the selenoprotein N (SEPN1) gene. A proportion of cases remain unresolved. Mutations in MYH7 encoding the beta myosin heavy chain protein have been implicated in cardiac and, less frequently, skeletal muscle disorders. Here we report four patients from two families with a histopathological diagnosis of MmD, presenting in childhood with slowly progressive muscle weakness, more proximal in Family 1 and more distal in Family 2, and variable degrees of cardiorespiratory impairment evolving later in life. There was also a strong family history of sudden death in the first family. Muscle biopsies obtained in early childhood showed multiple minicores as the most prominent feature. Sequencing of the MYH7 gene revealed heterozygous missense mutations, c.4399C>G; p.Leu1467Val (exon 32) in Family 1 and c.4763G>C; p.Arg1588Pro (exon 34) in Family 2.These findings suggest MYH7 mutations as another cause of a myopathy with multiple cores, in particular if associated with dominant inheritance and cardiac involvement. However, clinical features previously associated with this genetic background, namely a more distal distribution of weakness and an associated cardiomyopathy, may only evolve over time. © 2012 Elsevier B.V. Source

Singh R.R.,Neuromuscular Service | Tan S.V.,Neurology and Neurophysiology | Hanna M.G.,Center for Neuromuscular Disease | Robb S.A.,Institute of Child Health | And 3 more authors.

Laryngospasm is a rare but potentially life-threatening occurrence in infants and usually has infective, allergic, metabolic, or anatomic causes. Underlying genetic conditions are rarely considered. Mutations in SCN4A encoding the voltage-gated sodium channel NaV1.4 have been implicated in a wide spectrum of neuromuscular disorders with variable onset, ranging from a rare form of congenital myasthenic syndrome to both hypokalemic and hyperkalemic forms of periodic paralysis and paramyotonia congenita. Here we report on 3 unrelated patients without family history presenting with recurrent, life-threatening episodes of laryngospasm from the first months of life. Clinical features more typically associated with SCN4A-related disorders such as generalized muscle hypertrophy with clinical or electrical myotonia evolved later in life. All patients were found to be heterozygous for the same SCN4A mutation, c.3917G≥A; p.Gly1306Glu. Treatment with carbamazepine resulted in complete abolition of recurrent laryngospasm and alleviated symptoms associated with myotonia and muscle stiffness. We conclude that SCN4A mutations ought to be considered in the differential diagnosis of recurrent infantile laryngospasm because timely institution of treatment can be life-saving. Copyright © 2014 by the American Academy of Pediatrics. Source

Trump N.,DNA Laboratory | Cullup T.,DNA Laboratory | Verheij J.B.G.M.,University of Groningen | Manzur A.,University College London | And 4 more authors.
Neuromuscular Disorders

X-linked myotubular myopathy is a predominantly severe congenital myopathy with central nuclei on muscle biopsy due to mutations in the MTM1 gene encoding myotubularin. We report a boy with typical features of X-linked myotubular myopathy. Sequencing of the MTM1 gene did not reveal any causative mutations. Subsequent MLPA analysis identified a duplication of MTM1 exon 10 both in the patient and his mother. Additional quantitative fluorescent PCR and long-range PCR revealed an additional large deletion (2536. bp) within intron 10, 143. bp downstream of exon 10, and confirmed the duplication of exon 10. Our findings suggest that complex rearrangements have to be considered in typically affected males with X-linked myotubular myopathy. © 2011 Elsevier B.V. Source

Klein A.,University of Zurich | Klein A.,University College London | Jungbluth H.,Neuromuscular Service | Jungbluth H.,Kings College London | And 11 more authors.
Archives of Neurology

Objectives: To establish the consistency of the previously reported pattern of muscle involvement in a large cohort of patients with molecularly defined ryanodine receptor type 1 (RYR1)-related myopathies, to identify possible additional patterns, and to compare magnetic resonance imaging (MRI) findings with clinical and genetic findings. Design: Blinded analysis of muscle MRI patterns of patients with congenital myopathies with dominant or recessive RYR1 mutations and control patients without RYR1 mutations. We compared MRI findings with the previously reported pattern of muscle involvement. Setting: Data from 3 tertiary referral centers. Patients: Thirty-seven patients with dominant or recessive RYR1 mutations and 23 controls with other myopathies. Main Outcome Measures: Each MRI was classified as typical if it was identical to the reported pattern, consistentif it was similar to the reported one but with some additional features, or different. Images with no or few changes were classified as uninformative. Results: Twenty-one of 37 patients with RYR1 mutations had a typical pattern; 13 had a consistent pattern. Two patients had uninformative MRIs and only 1 had a different pattern. Compared with patients with dominant mutations, patients with recessive mutations and ophthalmoparesis had a more diffuse pattern, classified as consistent in 6 of 8. In contrast, 10 of 11 with recessive mutations but without ophthalmoparesis had a typical pattern. All MRIs of 23 control patients were classified as different. Conclusions: Our results suggest that muscle MRI is a powerful predictor of RYR1 involvement in patients with a congenital myopathy, especially if they carry a dominant mutation or recessive mutations without ophthalmoparesis. ©2011 American Medical Association. All rights reserved. Source

Wilmshurst J.M.,Red Cross | Lillis S.,Diagnostics Genetics Laboratory | Zhou H.,Institute of Child Health | Pillay K.,Red Cross | And 20 more authors.
Annals of Neurology

Objective Centronuclear myopathy (CNM) is a rare congenital myopathy characterized by prominence of central nuclei on muscle biopsy. CNM has been associated with mutations in MTM1, DNM2, and BIN1 but many cases remain genetically unresolved. RYR1 encodes the principal sarcoplasmic reticulum calcium release channel and has been implicated in various congenital myopathies. We investigated whether RYR1 mutations cause CNM. Methods We sequenced the entire RYR1 coding sequence in 24 patients with a diagnosis of CNM from South Africa (n = 14) and Europe (n = 10) and identified mutations in 17 patients. The most common genotypes featured compound heterozygosity for RYR1 missense mutations and mutations resulting in reduced protein expression, including intronic splice site and frameshift mutations. Results The high incidence in South African patients (n = 12/14) in conjunction with recurrent RYR1 mutations associated with common haplotypes suggested the presence of founder effects. In addition to central nuclei, prominent histopathological findings included (often multiple) internalized nuclei and type 1 fiber predominance and hypotrophy with relative type 2 hypertrophy. Although cores were not typically seen on oxidative stains, electron microscopy revealed subtle abnormalities in most cases. External ophthalmoplegia, proximal weakness, and bulbar involvement were prominent clinical findings. Interpretation Our findings expand the range of RYR1-related phenotypes and suggest RYR1 mutations as a common cause of congenital myopathies with central nuclei. Corresponding to recent observations in X-linked CNM, these findings indicate disturbed assembly and/or malfunction of the excitation-contraction machinery as a key mechanism in CNM and related myopathies. © American Neurological Association. Source

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