GLYCOGEN DISEASE OF SKELETAL MUSCLE

Abstract

Two cases of glycogen storage disease primarily affecting the skeletal muscle are presented. The patients were not related to each other, but both are from consanguineous families. In both cases a tentative clinical diagnosis was confirmed by skeletal muscle biopsy. Histologic studies of the skeletal muscle reveal a picture similar to that found in glycogen disease of the myocardium. Individual fibers show severe vacuolization with massive deposits of glycogen within the vacuoles. Large quantities of a basophilic material (presumably identical with that found in myocardial glycogenosis) are also found within the vacuoles. This material is characterized as an acid mucopolysaccharide; its histochemical and tinctorial properties are described. A method is given for avoiding the apparent discrepancy which may occur between the histochemical and biochemical estimations of glycogen content of skeletal muscle. The destruction of skeletal muscle is so severe and so extensive that the clinical signs of neurological involvement present in both our cases can be quite adequately and entirely accounted for by the local muscular damage. Previously reported cases of glycogen disease of skeletal muscle are reviewed. It was found that Werdnig-Hoffmann's progressive muscular atrophy could be distinguished from glycogen disease of skeletal muscle by the early appearance of pseudo-bulbar symptoms (especially dysphagia) in the latter disease. The relationship between the myocardial and the skeletal muscle forms of glycogen disease is discussed. Although clinically the 2 conditions may appear as 2 distinct entities, quantitative laboratory methods show considerable overlap in the 2 conditions. Skeletal muscle biopsy is indicated in every instance of progressive muscular weakness in order not to miss a possible case of glycogen storage disease primarily affecting skeletal muscle. The high glycogen content estimated biochemically and the histological picture described above are pathognomonic for this disease.