[Glycogen storage disease (Pompe's disease) presenting as myopathy in the adult (author's transl)].

In a 46-year-old woman with progressive atypical limb-girdle dystrophy for eight years the electromyogram revealed a myopathic pattern with signs of denervation activity. Enzymehistochemical and biochemical investigations of muscle and liver biopsies indicated type II glycogen storage disease (Pompe's disease). This type, with its prolonged course and the almost exclusive clinical involvement of proximal muscles mimics a "degenerative" neuromuscular disease, particularly muscle dystrophy, in the adult. Caused by acid maltase deficiency it is not a rare disease.