Subsarcolemmal vermiform deposits in skeletal muscle, associated with familial cardiomyopathy: report of two cases of a new entity.

Distinctive subsarcolemmal acid phosphatase-positive crescents were found in many muscle fibers of triceps muscle biopsies from 2 siblings with cardiomyopathy. The crescents appeared as dense osmophilic material in irregular vermiform arrays on electron microscopy. However, both patients had clinically normal skeletal muscle function. These 2 cases are believed to represent a rare familial myopathy affecting cardiac and skeletal muscle.