Hypouricemia due to renal tubular defect. A study with the probenecid-pyrazinamide test

Hypouricemia with hyperuricosuria due to isolated renal tubular defects are rare conditions. Two patients with hypouricemia and hyperuricosuria were studied for derangements in the renal urate transport with the combined probenecid-pyrazinamide test. In the first patient a significant decrease (64.5%) in the urate clearance--creatinine clearance ratio was noted after pyrazinamide administration, suggesting a post-secretory urate reabsorption defect, whereas the significant rise (44.2%) in urate clearance after the administration of probenecid indicates that this defect may not be complete. In the second patient there was a rise of 96.9% in the urate clearance--creatinine clearance ratio after the administration of probenecid and a decline of 31.6% in that ratio after pyrazinamide. These results suggest a defect in the presecretory reabsorptive site, with a highly significant response most probably of the postsecretory reabsorptive site to probenecid.