Hereditary xanthinuria: report of two cases.

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Hereditary xanthinuria is a rare disorder characterized by the replacement of uric acid by xanthine and hypoxanthine in urine . Two cases of classic hereditary xanthinuria in Taiwan are herein reported . Case 1 : a 30 -year -old woman was by chance found to have hypouricemia . Urine and plasma purines were checked through the use of high performance liquid chromatography . Urine excretion of uric acid was 0 .029 mumol (0 .005 mg )/mg creatinine (30 mumol /24 hr ); xanthine 1 .9 mumol /mg creatinine (1935 mumol /24 hr ); and hypoxanthine 0 .58 mumol /mg creatinine (587 mumol /24 hr ). Plasma xanthine was 9 .3 mumol /L ; hypoxanthine 5 .8 mumol /L ; and uric acid 0 .5 mumol /L (0 .001 mg /dL ). Case 2 : a brother of case 1 had a previous history of urolithiasis . Urine excretion of uric acid was 0 .15 mumol (0 .025 mg )/mg creatinine (189 mumol /24 hr ); xanthine 1 .3 mumol /mg creatinine (1620 mumol /24 hr ); and hypoxanthine 0 .22 mumol /mg creatinine (276 mumol /24 hr ).