Dominantly inherited cytoplasmic body myopathy in a Japanese kindred

An autosomal dominant progressive myopathy with diffuse cytoplasmic bodies (CBs) is described. In four successive generations, 12 patients suffered from weakness and atrophy of muscles in the distal extremities, neck, thorax and shoulder girdles. The mean age at onset was 42 years old, and the patients became disabled after 5 to 10 years due to chronic respiratory failure. The level of serum creatine kinase was normal or slightly elevated. An electromyogram showed a predominant myopathic change with a slight neurogenic change. Autopsy of 2 cases revealed numerous CBs in the skeletal muscles. Smooth and cardiac muscles were also affected. CBs were present predominantly in type I fibers in skeletal muscles. Males were more frequently affected than females (2:1). An electron microscopic examination showed dense central cores of myofilaments surrounded by radiating filaments. Characteristics of clinical course and histopathological findings in a new kindred are discussed in this rare disease.