Abstract
1. A case of Pompe's disease (glycogenosis II) without biochemically or histochemically demonstrable alpha-glucosidase activity is described. 2. Histochemical studies of skeletal muscle suggested that the glycogen is frequently stored as an acid mucopolysaccharide. 3. Electron microscopic studies revealed that the major glycogen deposits in most tissue were within membrane-limited sacs. Striated muscle was an exception because major deposits were frequently extrasaccular. 4. The findings in this case are discussed in relation to current concepts of Pompe's disease. In view of the extrasaccular glycogen deposits in skeletal muscle, it is suggested that an extralysosomal factor plays a significant role in the pathogenesis of Pompe's disease.