Hypouricemia due to an isolated defect in renal tubular urate reabsorption

During investigation of chronic glomerulonephritis, a 24-year-old man was found to have a low serum urate concentration (0.6-1.3 mg/100 ml). Daily urinary excretion of urate and oxypurines was normal. His urate clearance was markedly increased (43.3-98.0 ml/min), and was substantially unchanged after both the administration of pyrazinamide, an inhibitor of the renal tubular secretion of uric acid, and the administration of probenecid, an inhibitor of the renal tubular reabsorption of uric acid. No other renal tubular abnormalities were detected. It was concluded that the patient had an isolated defect in the renal tubular reabsorption of uric acid. The patient's brother was also found to have hypouricemia due to renal uricosuria, suggesting a genetic origin of the defect.