1/39. A clinical and genetic study of a manifesting heterozygote with X-linked myotubular myopathy.X-linked myotubular myopathy (XLMTM) characteristically causes severe or fatal muscle weakness in male infants. Mutations in the gene MTM1, encoding the protein myotubularin, can be identified in most families. Prior to this report, XLMTM was thought not to cause symptomatic manifestations in female carriers. We describe an adult female from a large family with typical XLMTM. The patient had progressive disabling muscle weakness of later onset and lesser severity than that observed in affected males. The distribution of weakness resembled typical XLMTM with facial weakness, marked limb-girdle weakness, respiratory muscle involvement and dysphagia. Analysis of the MTM1 gene identified a heterozygous missense mutation (G378R) within the highly conserved tyrosine phosphatase site of myotubularin. We did not identify significantly skewed X-inactivation. We conclude that XLMTM is capable of causing significant disability in heterozygotes.- - - - - - - - - - ranking = 1keywords = myopathy (Clic here for more details about this article) |
2/39. X-linked myotubular myopathy--a long-term follow-up study.X-Linked myotubular myopathy is a well delineated congenital myopathy, with a high neonatal and early childhood mortality. Only a single gene, mapping to Xq28 has been implicated and has recently been characterized. Phenotypic variability, both inter- and intrafamilial, has been recorded. Its severest expression is a uniform disease with polyhydramnios due to prenatal (neuromuscular) swallowing disorder, and partial inability to expand the lungs postnatally leading to early postnatal death in all. The mildest expression appears to be represented by the first family reported in the literature in which intrafamilial phenotypic variability was marked. There was neonatal asphyxia, but recovery took place in most affected patients and very mild expression permitting normal life into adulthood has been found in two patients. A long-term follow-up is given on both these families. Results emphasize the importance of the family history when trying to prognosticate in an individual case.- - - - - - - - - - ranking = 1.2keywords = myopathy (Clic here for more details about this article) |
3/39. Anaesthesia in myotubular (centronuclear) myopathy.A patient with a known history of myotubular myopathy presented for surgery for insertion of a tibial nail. Anasthesia was induced and maintained using an intravenous anasthetic technique. Neuromuscular function was assessed using mechanomyography, which showed a profound reduction in muscle contractility. In view of this, the use of muscle relaxants was avoided altogether. Nerve conduction was normal but electromyography showed small motor units, with generalised distribution, suggesting mild to moderately severe myopathy. The patient made a slow but uneventful recovery.- - - - - - - - - - ranking = 1.2keywords = myopathy (Clic here for more details about this article) |
4/39. alternative splicing of exon 17 and a missense mutation in exon 20 of the insulin receptor gene in two brothers with a novel syndrome of insulin resistance (congenital fiber-type disproportion myopathy).The insulin receptor (IR) in two brothers with a rare syndrome of congenital muscle fiber type disproportion myopathy (CFTDM) associated with diabetes and severe insulin resistance was studied. By direct sequencing of Epstein-Barr virus-transformed lymphocytes both patients were found to be compound heterozygotes for mutations in the IR gene. The maternal allele was alternatively spliced in exon 17 due to a point mutation in the -1 donor splice site of the exon. The abnormal skipping of exon 17 shifts the amino acid reading frame and leads to a truncated IR, missing the entire tyrosine kinase domain. In the correct spliced variant, the point mutation is silent and results in a normally translated IR. The paternal allele carries a missense mutation in the tyrosine kinase domain. All three cDNA variants were present in the lymphocytes of the patients. Purified IR from 293 cells overexpressing either of the two mutated receptors lacked basal or stimulated IR beta-subunit autophosphorylation. A third brother who inherited both normal alleles has an normal muscle phenotype and insulin sensitivity, suggesting a direct linkage of these IR mutations with the CFTDM phenotype.- - - - - - - - - - ranking = 1keywords = myopathy (Clic here for more details about this article) |
5/39. temporomandibular joint involvement in a patient with centronuclear myopathy.We describe here the temporomandibular joint and masticatory muscle abnormalities disclosed by computed tomography and magnetic resonance imaging in a 25-year-old man with centronuclear myopathy (a congenital myopathy) who presented with marked limitation of jaw movements. We found an intense and general fatty replacement of the masticatory muscles, and magnetic resonance imaging signals indicated articular fibrosis. We conclude that in centronuclear myopathy, the presence of weakness and hypomotility of the masticatory muscles can induce chronic abnormalities of the temporomandibular joint.- - - - - - - - - - ranking = 1.4keywords = myopathy (Clic here for more details about this article) |
6/39. Diagnostic challenges in combined multiple sclerosis and centronuclear myopathy.The first case of combined centronuclear myopathy and multiple sclerosis is reported. The difficulties of diagnosing multiple sclerosis in patients with muscular disorders associated with the central nervous system involvement are discussed.- - - - - - - - - - ranking = 1keywords = myopathy (Clic here for more details about this article) |
7/39. Hitherto undescribed venous vacuolar myopathy without mucoid degeneration in the varicose saphenous vein of a child.Varicose vein abnormalities involving the lesser saphenous vein of a 7-year-old boy are presented. The histopathology of the vein wall revealed a vacuolar degeneration without mucoid deposits of the muscle cells, which has not been described previously in the literature in congenital varices.- - - - - - - - - - ranking = 0.8keywords = myopathy (Clic here for more details about this article) |
8/39. A double mutation in a patient with X-linked myotubular myopathy.In this report a double mutation was identified in a patient with X-linked myotubular myopathy. The mutations present in the patient were a C-->T substitution of nucleotide 163, which led to an Arg 55 stop codon (nonsense mutation), and an "A" insertion at nucleotide 440, which caused a shift of the reading frame and a premature stop at codon 153 (frameshift mutation). The nonsense mutation was heterozygously present in the mother but not identified in the father or in normal controls. The frameshift mutation was not identified in either parent or normal controls (de novo mutation). These mutations are predicted to truncate the myotubularin protein.- - - - - - - - - - ranking = 1keywords = myopathy (Clic here for more details about this article) |
9/39. Reducing body myopathy with cytoplasmic bodies and rigid spine syndrome: a mixed congenital myopathy.At the age of five years a male child started to develop a progressive rigid spine, torsion scoliosis, and flexion contractures of his elbows, knees, hips, and ankles owing to severe proximal and distal muscle weakness. He had three muscle biopsies from three different muscles at ages 7, 11, and 14 years, respectively. Myopathologically, these muscle tissues contained numerous inclusions which, at the ultrastructural level, turned out to be reducing bodies and cytoplasmic bodies, often in close spatial proximity. Similar histological inclusions, although not further identified by histochemistry and electron microscopy, were seen in his maternal grandmother's biopsied muscle tissue who had developed weakness of the legs and hands after the age of 50 years. The patient's parents were healthy, but the mother's quadriceps muscle showed an increased spectrum of muscle fibre diameters. Our patient, thus, had a neuromuscular disorder, perhaps familial, presenting as a mixed congenital myopathy, i.e., reducing body myopathy with cytoplasmic bodies, of which the morphological lesions could be consistently documented over several years in his different limb muscles. While other mixed congenital myopathies had shown cores and rods, both related to sarcomeres and thus possibly morphogenetically related, cytoplasmic bodies thought to be related to Z-bands and reducing bodies dissimilar to any muscle fibre constituent do not share any common denominator. Therefore, we suggest that this neuromuscular disorder may be a unique mixed congenital myopathy, either sporadic or genetic. In the latter case, the transmission pattern suggested X-linked recessive inheritance, but an autosomal-dominant transmission with variable penetrance could not be ruled out.- - - - - - - - - - ranking = 2.2keywords = myopathy (Clic here for more details about this article) |
10/39. Structural and functional analysis of a new desmin variant causing desmin-related myopathy.desmin-related myopathy is a familial or sporadic disease characterized by skeletal muscle weakness and cardiomyopathy as well as the presence of intracytoplasmic aggregates of desmin-reactive material in the muscle cells. Previously, two kinds of deletions and eight missense mutations have been identified in the desmin gene and proven to be responsible for the disorder. The present study was conducted to determine structural and functional defects in a pathogenic desmin variant that caused a disabling disorder in an isolated case presenting with distal and proximal limb muscle weakness and cardiomyopathy. We identified a novel heterozygous Q389P desmin mutation located at the C-terminal part of the rod domain as the causative mutation in this case. transfection of desmin cDNA containing the patient's mutation into C2.7, MCF7, and SW13 cells demonstrated that the Q389P mutant is incapable of constructing a functional intermediate filament network and has a dominant negative effect on filament formation. We conclude that Q389P mutation is the molecular event leading to the development of desmin-related myopathy.- - - - - - - - - - ranking = 1.6keywords = myopathy (Clic here for more details about this article) |
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