A 48, XXYY syndrome, a rare variant of Klinefelter's syndrome, was recognized through chromosome analysis in a 34-year-old Japanese male with hypogonadism. On routine laboratory examinations, he also had hypouricemia (1.7-2.6 mg/dl). Oral administration of inosine resulted in increases in serum and urinary urate concentrations, suggesting that endogenous urate synthesis from inosine was not disturbed. Renal clearance ratio of urate to creatinine (CUA/Ccr) increased markedly after an oral administration of probenecid. The decrease in CUA/Ccr after pyrazinamide administration seemed almost normal.
The above data show that the hypouricemia in the patient is due to the isolated renal tubular abnormality. Several mechanisms for renal hypouricemia have been proposed which include three types of reabsorption defect and an abnormality with increased urate secretion. The present patient would be considered to be a case of incresed renal tubular urate secretion.
The family study has suggested that the renal hypouricemia in this patient is of hereditary nature. Further investigations are needed to elucidate whether any etiological relationship exists betweeen renal hypouricemia and XXYY syndrome.
