M complications in long-term survivors with X-linked myotubular myopathy

X-linked myotubular myopathy (McKusick no. 31040) is a congenital myopathy in which affected male subjects typically present with severe hypotonia and respiratory distress at birth. Surviving patients have prolonged ventilator dependence and grossly delayed motor milestones but usually have intact intelligence.1-3 However, the long-term prognosis as reported in the literature is generally poor, and withdrawal of ventilatory support for affected infants is not uncommon. Diagnosis of MTM1 has relied on a positive family history and the demonstration of the presence of characteristic central nuclei resembling fetal myotubes in muscle biopsy specimens from affected male subjects, as well as the exclusion of congenital myotonic dystrophy.4 Autosomal forms of MTM have also been described1,3 but are reported to have a milder phenotype than the X-linked form.