Renal hypouricemia の2例における腎の尿酸処理の検討

抄録

We presented two patients associated with hypouricemia. Their serum uric acid levels were 1.6 and 1.3 mg/100ml, respectively. One patient,28 aged female, had a history of urolithiasis and showed microhematuria. Another,47 aged female, had mild hypertension and microhematuria. No other family members have been proven to have hypouricemia. These two patients gave markedly increased urate clearance and normal G F R. Other findings which indicate renal tubular dysfunction, such as glycosuria, amino aciduria, decreased phosphate reabsorption and renal tubular acidosis, were not demonstrated in them. Hypercalciuria was also not be detected.
In pyrazinalnide (PZA) suppression test, these two showed different response of urate excretion. In one patient urate excretion was slightly suppressed following PZA administration. Following benzbromarone, which inhits urate reabsorption in the tubule, urate excretion almost unchanged. This patient is considered to have a defect of urate reabsorption in the proximal tubule, resulting renal urate wasting.
Another patient, on the other hand, showed marked decrease of urate excretion following PZA. This result suggests that increased urate clearance in this patient is due to either enhanced secretion or diminished reabsorption of secreted urate in the tubule. Uricosuric response to benzbromarone was far lesser than in seven normal controls. Suppression rate of urate excretion following PZA under benzbromarone-induced uricosuria was similar to the value of normals. These results suggest that this patient has a defect of postsecretory reabsorption of urate in the tubule, but not enhanced secretion of urate.
Renal uricosuria with hypouricemia is a rare disease and it is considered that there are some subtypes of urate transport defect which cuases renal urate wasting.