Distal Myopathy of Miyoshi Type: 1 Case

ABSTRACT

Miyoshi myopathy (MM) is a type of distal myopathy that is characterized by an early adult onset and a prominent involvement of the gastrocnemius muscles. Weakness usually appears between 15 and 30 years of age starting in the posterior compartment of the legs. Creatine kinase (CK) values are characteristically elevated to levels 10 to 100 fold above normal range. Here we report one patient who was diagnosed as MM. She developed a motor weakness in her early thirties. There was an early and predominant involvement of the gastrocnemius muscles. Creatine kinase activity was elevated 10 to 15 fold above normal range. Electromyography revealed fibrillations, positive sharp waves, and a myopathic pattern of motor unit potentials, particularly in the distal muscles of the lower limbs. Myopathic features without vacuoles were seen in the vastus lateralis muscle. This is the first case report of MM in Korea, which should be considered in the differential diagnosis of slowly progressive weakness of distal legs.