Renal hypouricemia: incomplete combined defect.

A 20-year-old man with hypouricemia with markedly increased renal uric acid clearance is described. He also exhibited idiopathic hypercalciuria and lipoid nephrosis on hospital admission. Urate excretion was minimally suppressed by pyrazinamide and minimally increased after administration of probenecid, whereas it decreased after administration of benzbromarone. These results suggest that not only presecretory reabsorption, but also postsecretory reabsorption of urate was incompletely defective and indicate that the latter is more defective than the former. The relationship between hypouricemia and hypercalciuria or lipoid nephrosis in this case is not clear. However, since the hypouricemia persisted despite the remission of minimal change nephrotic syndrome, it appears that at least his nephrosis was incidental.