Mechanism of Hypouricemia in a Child with the Normotensive Form of Gordon's Syndrome

The mechanism of renal tubular urate transport disorder was studied by the pyrazinamide and probenecid tests in a 12-year-old hypouricemic boy suffering from the normotensive form of Gordon's syndrome, with increased distal tubular reabsorption of NaCl (confirmed by the hypotonic saline diuresis test). The aim of the study was to determine the impact of oral hydration during the tests on the phases of renal tubular urate transport: before (I), and during long-term hydrochlorothiazide therapy (0.5 mg/kg BW/day) (II). In both periods (I,II), presecretory reabsorption of urate was within normal limits. Hypouricemia in our patient was caused by decreased postsecretory reabsorption, with or without simultaneous increase of tubular urate secretion. The degree of overhydration determines which of these mechanisms is responsible for increased renal urate clearance.