An in-crease of the serum uric acid and hypoxanthine concentration in patients with myocardial infarction indicates a significant metabolic involvement of xanthine oxidoreductase in this disease and therefore a possible role in the development of tissue damage in the postischaemic phase due to oxygen radicals generated by the oxidase activity of this enzyme [40,41]. The gene discussed is XDH; the disease is myocardial infarction.