Hepatic involvement in a case of lysosomal glycogen storage disease with normal acid maltase

A 19-year-old man, who could run only slowly since childhood and who walked on his toes since 12 years of age, noted difficulty in climbing upstairs at 17 years of age. He was admitted to Kyushu University Hospital because of elevated AST, ALT and CK levels. On admission, the liver was palpable two fingerbreadths beneath the right costal margin. A neurological examination revealed a low IQ on WAIS-R, a decreased muscle tonus in his four limbs, moderate weakness of the neck flexor and bilateral tibialis anterior muscles, contracture of the ankle joints, and bilateral pes cavus. The serum CK was elevated to 1,124U/l. Hepatic enzymes, such as AST, ALT, LDH and γ- GTP were also moderately increased in the sera. A needle EMG disclosed myogenic patterns in the limb muscles. Biopsied biceps brachii muscle showed a mild variation in the fiber size and multiple tiny vacuoles in 5-10% of the muscle fibers. PAS and acid phosphatase were strongly positive in some vacuoles. On electron microscopy, numerous autophagic vacuoles containing glycogen granules were observed. The acid maltase activities were, however, normal in the peripheral blood lymphocytes, the biopsied muscle, and the cultured skin fibroblasts. He was thus diagnosed to have lysosomal glycogen storage disease with normal acid maltase. A histological examination of the biopsied liver revealed the portal and central veins to be slightly sclerotic. In addition, mild fatty changes and frequent nuclear vacuolization were present in the hepatocytes. On electron microscopy, enlarged mitochondria with irregular cristae were also observed. Due to the fact that the cardiac function was well preserved, these hepatic lesions were thought to result from the metabolic abnormalities underlying in this disorder.