A rare case of centronuclear myopathy with DNM2 mutation: genotype­phenotype correlation

Centronuclear myopathy (CNM) is a group of rare genetic muscle disorders characterized by muscle fibers with centrally located nuclei. The most common forms of CNM have been attributed to X-linked recessive mutations in the MTM1 gene; autosomal-dominant mutations in the DNM2 gene-encoding dynamin-2, the BIN1 gene; and autosomal-recessive mutations in BIN1, RYR1, and TTN genes. Dominant CNM due to DNM2 mutations usually follows a mild clinical course with the onset in adolescence. Currently, around 35 mutations of the DNM2 gene have been identified in CNM; however, the underlying molecular mechanism of DNM2 mutation in the pathology of CNM remains elusive, and the standard clinical characteristics have not yet been defined. Here, we describe the case of a 17-year-old female who presented with proximal muscle weakness along with congenital anomalous pulmonary venous connection (which has not been described in previous cases of CNM), scoliosis, and lung disease without a significant family history. Her creatine kinase level was normal. Histology, special stains, and electron microscope findings on her skeletal muscle biopsy showed CNM with the characteristic features of a DNM2 mutation, which was later confirmed by next-generation sequencing. This case expands the known clinical and pathological findings of CNM with DNM2 gene mutation.

A family with dynamin 2-related centronuclear myopathy without ocular involvement

Centronuclear myopathy (CNM) is a rare congenital myopathy that is pathologically characterized by the centrally locatednuclei in most of the muscle fibers. On clinical examination, dynamin 2 (DNM2)-related CNM typically shows distaldominant muscle atrophy, ptosis, ophthalmoplegia, and contracture. The reported cases of CNM in Caucasian studies showa high prevalence rate of early-onset ptosis and ophthalmoplegia and correlated with the severity of the disease. However,Asian reports show a low prevalence and late-onset ocular symptoms in DNM2-related CNM patients. p.R465W is one ofthe most commonly found mutations in Western countries, and all the cases showed ocular symptoms. The proband and hisdaughter had no ocular symptoms despite harboring the same p.R465W mutation. This family makes us speculate that ocularsymptoms in DNM2-related CNM are influenced by ethnic background. In addition, this is the first familial case of DNM2-related CNM in Korea.

Estudo clínico, histológico e molecular da miopatia centronuclear / A clinical, histological and molecular study of centronuclear myopathy

Introdução: A miopatia centronuclear é uma doença muscular congênita com apresentação clínica heterogênea, caracterizada histologicamente pela proeminência de fibras musculares com núcleos centralizados. Três formas são reconhecidas: neonatal grave, com herança ligada ao X e envolvimento do gene MTM1; autossômica dominante, com início geralmente tardio e curso mais leve, associada a mutações no gene DNM2; e autossômica recessiva, com gravidade intermediária entre as outras formas e envolvimento dos genes BIN1, RYR1 ou TTN. Apesar da identificação dos principais genes responsáveis pela doença, os métodos usuais de diagnóstico genético não encontram mutações em cerca da metade dos casos. Objetivo: O objetivo deste estudo foi a caracterização clínica, histológica e molecular de pacientes brasileiros portadores de miopatia centronuclear. Métodos: Laudos de dois bancos de biópsia muscular foram usados para identificar pacientes com diagnóstico de miopatia centronuclear nos últimos dez anos. As lâminas das biópsias foram revisadas e analisadas, e as famílias correspondentes convocadas para aplicação de protocolo clínico e coleta de sangue periférico para extração de DNA genômico. As famílias foram estudadas para os genes conhecidos por sequenciamento Sanger, MLPA, painel de genes implicados em doenças neuromusculares ou sequenciamento de exoma. Resultados: Foram convocados 24 pacientes provenientes de 21 famílias, em 16 das quais foi possível estabelecer o diagnóstico molecular. As 7 famílias com a forma neonatal grave constituíam um grupo homogêneo clínica e histologicamente, e mutações novas e conhecidas foram encontradas no gene MTM1 em 6 destas. Dois meninos deste grupo, com evolução estável, tiveram óbito súbito por choque hipovolêmico subsequente a rompimento de cisto hepático. O gene MTM1 também foi implicado em uma menina portadora manifestante, com quadro mais leve, na forma de uma macrodeleção em heterozigose, detectada por MPLA...

Introduction: Centronuclear myopathy is a heterogeneous congenital muscle disease, characterized by the prominence of centralized nuclei in muscle fibers. Three disease forms are recognized: a severe neonatal, X-linked form caused by mutations in the MTM1 gene; an autosomal dominant, late-onset milder form, associated to the DNM2 gene; and an autosomal recessive form, with intermediate severity, so far with the BIN1, RYR1 or TTN genes implicated. In spite of the identification of these genes, usual molecular diagnostic methods don't yield a molecular diagnosis in about half of cases. Objetives: The aim of this work was to study clinical, histological, and molecular aspects of centronuclear myopathy Brazilian patients. Methods: Reports taken from two muscle biopsy banks were used to identify centronuclear myopathy patients in the last ten years. Biopsy slides were reviewed and analyzed, and corresponding families recruited to apply a clinical protocol and to draw peripheral blood to extract genomic DNA. Families were studied for known genes via Sanger sequencing, MLPA, panel of genes implicated in neuromuscular diseases, or exome sequencing. Results: Twentyfour patients out of 21 families were recruited, and in 16 families molecular diagnosis was established. The 7 families with the severe neonatal form amounted to a clinically and histologically homogeneous group, and mutations, both known and novel, were found in the MTM1 gene in 6 of these. Two boys of this group, with a stable course, died suddenly of hypovolemic shock due to a hepatic cyst rupture. The MTM1 gene was also implicated in the case of a mild manifesting carrier girl with a heterozygous macrodeletion detected via MLPA...

Clinical and Pathological Features of Korean Patients with DNM2-Related Centronuclear Myopathy

BACKGROUND AND PURPOSE: Centronuclear myopathy (CNM) is characterized by the presence of central nuclei within a large number of muscle fibers. Mutations of the dynamin 2 gene (DNM2) are common causes of autosomal dominant or sporadic CNM. The aim of this study was to characterize the clinical and pathological features of CNM relative to the presence of DNM2 mutations. METHODS: Six patients with clinical and pathological features of CNM were recruited. Detailed clinical and pathological findings were analyzed according to the presence of DNM2 mutations. RESULTS: We detected DNM2 mutations in four of the six sporadic CNM patients, and identified the following distinct clinical and pathological features in those patients with DNM2 mutations: preferential involvement of the distal lower limbs, typical nuclear centralization, and radially distributed sarcoplasmic strands in muscle pathology. In contrast, those without DNM2 mutations exhibited rather diffuse muscular involvement, and nuclear internalization and myofibrillar disorganization were more pronounced features of their muscle pathology. CONCLUSIONS: These findings suggest the presence of specific features in Korean CNM patients. A detailed clinical and pathological examination of CNM patients would be helpful for molecular genetic analyses of this condition.

Clinical and pathological features of 16 patients with centronuclear myopathy / 中华神经科杂志

Objective To analyze and summarize the clinical , pathological features of 16 patients with centronuclear myopathy.Methods All of the 16 patients performed clinical examination and sporadic patients and a proband with family history ( n=6 ) performed serum creatine kinase , electromyography and open muscle biopsies , and the specimens were used for a standard series of histological and histochemical stainings.The clinical and pathological features of these patients were analyzed.Results The proportion of centronuclear myopathy in suspected myopathy cases was 0.127%(6/4 724) in our department.The onset time ranged from infancy to adulthood.The common initial symptoms included mild to moderate weakness of lower limbs and bilateral ptosis ( n =4 ).The other symptoms were facial weakness ( n =1 ) and ophthalmoplegia (n=1).There were 12 patients performing distal weakness exceeding proximal weakness . One family with autosomal dominant inheritance of 11 patients had a later age of onset than the sporadic ones and manifested bilateral ptosis , bilateral lower limbs weakness , especially in distal muscle.Muscle biopsies showed pronouncedly increased amount of fibers with centrally placed nuclei with predominant type Ⅰfibers and a clear perinuclear halo surrounding the centrally placed nuclei and an appearance of spoke of a wheel in some fibers.Conclusions This series of centronuclear myopathy patients manifest clinical heterogeneity.Muscle biopsies show features of centralized nuclei pronounced increase , type Ⅰfibers predominance , etc.These can provide evidences for the diagnosis of the disease.

Two Cases of X-Linked Myotubular Myopathy with Novel MTM1 Mutations

BACKGROUND: Myotubular myopathy (MTM) is a congenital myopathy characterized by centrally placed nuclei in muscle fibers. Mutations in the myotubularin 1 gene (MTM1) have been identified in the most of the patients with the X-linked recessive form. CASE REPORT: This report describes two male infants with X-linked MTM (XLMTM). Both patients presented with generalized hypotonia and respiratory difficulties since birth. We did not perform a muscle biopsy in either patient, but their conditions were diagnosed by genetic testing of MTM1. One splicing mutation, c.63+1G>C, and a frame-shift mutation, c.473delA (p. Lys158SerfxX28), were identified. Neither mutation has been reported previously. CONCLUSIONS: Genetic testing for MTM1 is helpful for the differential diagnosis of floppy male infants. We suggest that advanced molecular genetic testing may permit a correct diagnosis while avoiding invasive procedures.

X-linked Myotubular Myopathy in a Family with Two Infant Siblings: A Case with MTM1 Mutation

X-linked myotubular myopathy (XLMTM) is a rare congenital muscle disorder, caused by mutations in the MTM1 gene. Affected male infants present severe hypotonia, and generalized muscle weakness, and the disorder is most often complicated by respiratory failure. Herein, we describe a family with 2 infants with XLMTM which was diagnosed by gene analysis and muscle biopsy. In both cases, histological findings of muscle showed severely hypoplastic muscle fibers with centrally placed nuclei. From the family gene analysis, the Arg486STOP mutation in the MTM1 gene was confirmed.

A Case of Centronuclear Myopathy

Centronuclear myopathy is a rare congenital myopathy, which is characterized by centrally located nuclei and hypotrophy or predominance of type 1 fibers in muscle pathology. It is classified into three forms according to the clinical features and inheritance pattern: the X-linked recessive, the autosomal recessive, and the autosomal dominant forms. We report a case of a patient with generalized muscle weakness, poor muscle bulk, and dysmorphic features who was diagnosed as centronuclear myopathy.

A Case of Adult-Onset Centronuclear Myopathy

Centronuclear myopathy (CNM) is a rare congenital myopathy that is characterized by centrally placed nuclei in the muscle fibers. Based on the time of onset and the mode of inheritance, CNM can be divided into three distinct forms: the severe neonatal form, the childhood onset form, and the adult onset form. This paper describes the case of a female patient with CNM, in whom the disease manifested itself in the fifth decade of life, without any prior family history of such disorders. To the best of our knowledge, this is a rare case of late adult-onset CNM.

Familial Myotubular Myopathy Occurred in a Sibling / 대한소아신경학회지

Myotubular or centronuclear myopathy(MTM) is a rare congenital myopathy, which is characterized by predominance and atrophy of type 1 fibers and centrally located nuclei in muscle pathology. The clinical features and severity are quite variable. MTM is classified as three forms according to the inheritance pattern : autosomal dominant, autosomal recessive and X-linked recessive. The authors present familial myotubular myopathy, suggestive of X linked, occurred in a sibling with intrafamilial clinical variability.

Myotubular myopathy: A case report

A case of a myotubular myopathy in a 5 year old boy is described. This was the first and the only boy to a 30 year old mother who had no prenatal or perinatal problems. No family history of muscle disease was present. His muscle weakness started from neonatal period but was very slowly progressive. The developmental milestones were generally delayed. He had repeated episodes of pneumonia. Muscle biopsy revealed characteristic cental nuclei in 68% of myofibers, and this findings was associated with generally small and round fibers and minimal interstitial change. No inflammatory reaction was present.