Electron microscopy of skin specimens of five patients with glycogenosis type III were correlated with clinical, biochemical, and electrophysiological findings from the Divisions of Neuropathology and Neuropediatrics, Ciudad Sanitaria Valle de Hebron, Barcelona, Spain. The disease began in infancy in four patients and at 38 years of age in one adult patient. Massive glycogen storage was observed in epithelial secretory cells of eccrine sweat glands and other cells, including Schwann cells of myelinated and unmyelinated fibers, were not affected. The changes differed clearly from those in glycogenosis II where glycogen storage is membrane bound and is found in most skin cells including fibroblasts, sweat glands, smooth muscle fibers, endothelial cells, and Schwann cells. Skin biopsy appeared to be useful in diagnosis of glycogenosis III and its differentiation from other glycogen storage disorders. 
COMMENT. Glycogen storage disease type III (debrancher deficiency, Cori-Forbes disease) is an autosomal recessively inherited disease with a deficiency in amy1-1, 6-glycosidase or debrancher enzyme. Enzyme deficiencies occur in liver, muscle, heart, leukocytes, erythrocytes, fibroblasts, and muscle cultures. Abnormal glycogen storage is found in liver, muscle, and erythrocytes. Clinically there are three types, 1) infantile, 2) childhood, 3) adult type. The infantile type is associated with hypoglycemia, failure to thrive, and hepatomegaly. Symptoms usually remit partially with growth. Childhood types present with heart failure and exercise intolerance. Adults develop gradual weakness and wasting of distal muscles and may have a history of abdominal enlargement with hepatic dysfunction in early childhood. EMG shows diffuse myopathic changes. Growth failure and hepatic dysfunction including hypoglycemia have been improved by the administration of cornstarch.