Familial nemaline myopathy

Two sisters with congenital nemaline myopathy are described. In both cases almost 70% of muscle fibers contained rods which were selectively localized in the larger ones. The variability coefficient was abnormally increased. Histochemical reactions showed that almost all the muscle fibers were type 1. In one case many fibers contained one or more core-like lesions. The parents and two siblings of the patients were clinically normal; EMG examination also showed normal motor unit potentials. Muscle biopsy was normal in the father; in the mother a slight type 1 predominance was detected without rods or other signs of myopathy. The disease seems to be transmitted by an autosomal recessive trait, although incomplete penetrance of a dominant trait cannot be excluded.