To elucidate the pathogenesis of hyperuricemia in type VII glycogenosis (muscle and erythrocyte phosphofructokinase deficiency), we studied the effect of exercise on purine catabolism in the muscle in two unrelated patients with this disorder. The patients performed semi-ischemic forearm exercise tests and metabolites appearing in cubital venous blood were measured. In contrast to the lack of increase in lactate, marked increases in ammonia, inosine and hypoxanthine were observed in both patients. These findings demonstrated there is an accelerated purine degradation in exercising muscle of type VII glycogenosis. Inosine and hypoxanthine are precursors for uric acid synthesis. We propose that the enhanced production of mosine and hypoxanthine in muscle and their subsequent release from muscle are responsible for the development of hyperuricemia in type VII glycogenosis.
