抄録
X-linked myotubular myopathy (XLMTM) is a congenital myopathy characterized by severe hypotonia and muscle weakness, and respiratory insufficiency after birth. Surviving patients have prolonged ventilator dependence and severely delayed motor milestones. Myotubularin, which is encoded by MTMI gene, is a new family of putative tyrosine phosphatase and appears to be ubiquitously expressed, with a 3.9 kb transcript detected in all adult and fetal tissues studied. The mutations in XLMTM are occurred in all exons, and the types of them are various. These mutations caused a development of an inactivation of the putative enzymatic activity of myotubularin. We present clinical and molecular analysis of two patients with XLMTM in which we identified mutations of the MTMI gene. ln one patient, an AAAG deletion was identified at the position of nucleotide 193 in coding exon 4. These 4 bp deletions caused a shift of the reading frame and created a stop codon (frameshift mutation). His mother had both normal and mutant alleles heterozygously as a XLMTM carrier. In another patient, a C to T substitution of nucleotide 163, leading Arg 55 to stop codon (nonsense mutation) was identified. His mother, who was an identical twin, had both norma1 and mutant alleles heterozygously as a XLMTM carrier.
