Minicore myopathy with dominant inheritance.

Minicore disease (multicore disease) is a benign myopathy characterized by segmental muscle fibre degeneration with disruption of myofibrils and loss of mitochondria. The disease is generally thought to occur either sporadically or follow an autosomal recessive mode of inheritance. We describe 2 patients, a mother and her son, with essentially non-progressive weakness of both proximal and distal muscles. Biopsies from both patients showed focal defects of oxidative enzyme activity as well as focal disturbances of cross-striation typical of minicore myopathy. Normal fibre type differentiation was lacking. Three other families reported in the literature suggest dominant inheritance of minicore myopathy or closely related disease.