X-linked myotubular myopathy with fatal neonatal asphyxia.

A second family with X-linked myotubular myopathy is described. The clinical picture includes decreased fetal movements; hydramnios, in at least three cases, probably resulting from insufficient swallowing in utero; and asphyxia at birth. In three autopsy cases many myotubes were found in the muscle tissue. In five definite female carriers, muscle biopsy revealed changes, including myotubes in four. This family probably is not related to the eariler described family with X-linked myotubular myopathy, from which it differs in its 100 percent fatal outcome in the neonatal period, as compared with 25 percent in the eariler described family. A most important finding, in both families, is the possibility of recognizing clinically healthy female carriers by muscle biopsy.