Nemaline myopathy and a mitochondrial neuromuscular disorder in one family.

A family composed of parents and four children is reported. Two brothers presented from early infancy with hypotonia and non-progressive weakness. Muscle biopsy in both revealed numerous typical nemaline rods. The father, suffering from backache, had a slow MNCV of both common peroneal nerves. His muscle revealed variation in fiber size, splitting, type 1 atrophy and numerous pleomorphic mitochondria with crystalline inclusions. The mother's muscle showed type 2 atrophy, foci of myofibrillar degeneration, and lipofuscin bodies. In a 12-year-old daughter and a 5-year-old son the muscle revealed an excess of small, bizarre mitochondria and lipid droplets. The coexistence of nemaline myopathy and a mitochondrial neuromuscular disorder in one family has never been reported in the literature. It might be a coincidence of two rare muscle disorders in one family, or it might be the polymorphic expression of a single etiological factor causing a defect in protein synthesis.