Distal muscular dystrophy of Miyoshi type. Report of two cases and review of the literature.

Miyoshi myopathy (MM) is a rare distal myopathy that mainly occurs in Japan. And that is characterized by prominent involvement of the gastrocnemius muscles. Here we report two patients, brother and sister, from a German family. Onset of the disease was at the age of 20 and 22 years, respectively. In both siblings, there was an early and predominant involvement of the gastrocnemius muscles. Creatine kinase activity was elevated 37- to 95-fold above normal. Electromyography revealed fibrillations, positive sharp waves and a myopathic pattern, particularly in the distal muscles of the lower limbs. Histology of the gastrocnemius muscles showed myopathic changes consistent with muscular dystrophy. Occurrence in these two siblings but in no other family members was indicative of an autosomal-recessive inheritance. Our report indicates that MM may also be found in Germany, and that it should be considered in the differential diagnosis of distal myopathies.