[A study of the abnormal polysaccharide in a child with type IV glycogen storage disease (author's transl)].

In type IV glycogen storage disease, the abnormal storage material is a partially amylase-resistant, PAS-positive polysaccharide and a deficiency of the branching enzyme is present in virtually all cases studied so far. Electron microscopic, biochemical and enzymatic studies were carried out in a child presenting with the clinical and histological features of this disease. Electron microscopic study showed the amylase-resistant material to be fibrillar and poorly soluble in buffers. Iodine spectrum analysis indicated that the lambda max of the liver polysaccharide was between that of normal glycogen and that of typical type IV glycogen. Branching enzyme activity was not detectable in the patient's leucocytes but was close to normal in the liver and clearly detectable in cultured fibroblasts. These results suggest that the absolute value of the deficiency of the branching enzyme in the liver of patients with type IV glycogen storage disease could be questioned. Alternatively this patient as well as another one reported in the literature could be considered as subtypes of the disease in whom liver and fibroblast branching enzyme activity remains detectable in vitro.