[Cousins with X-linked recessive myotubular myopathy]

We describe two cousins with severe infantile form of myotubular myopathy. In Japan this disease has previously been reported in only three families. Case 1. The propositus, a 2-year-5-month-old boy, had been on a respirator since birth. He had a history of severe neonatal asphyxia and sequential hypotonia with dyspnea. Findings diagnostic of congenital myotubular myopathy, such as central nuclei and peripheral halo of muscle fibers, were demonstrated in his biopsied muscle. Case 2. A male the cousin of case 1 had congenital myopathy and died at 3 months of age due to respiratory failure. His muscle biopsy disclosed the identical findings as had been seen in case 1. These two cases were born to twin mothers, suggesting X-linked recessive inheritance. Early diagnosis and proper treatment of myotubular myopathy are important, because this condition may be erroneously-interpreted as the sequelae of neonatal asphyxia.