Type III glycogenosis." Atypical in blood cells in two siblings enzyme activities

Two siblings with the clinical features of glycogen storage disease are described. Glucagon tolerance tests revealed a nonsignificant rise in blood sugar above fasting levels, whereas intravenous administration of galactose resulted in a normal increase in blood glucose. Amyloglucosidase (debraneher enzyme) activity was absent in liver and muscles as assayed by incorporation of U-I+C glucose and by release of glucose from a phosphorylase limit dextrin. Incorporation of U-I+C glucose, although reduced, occurred in leukocytes and was normal in erythrocytes. Transferase activity was present in muscle and liver but absent in leukocytes. Assay of enzyme activity in blood cells only, as a means of diagnosing type II1 glycogenosis, may be misleading.