[Hereditary xanthinuria, rare cause of hypo-uric acidemia. 2 cases].

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Hypouricemia can be observed in uncommon situations as in our two patients with hereditary xanthinuria .In the first case , hereditary xanthinuria was discovered in a 36 -year -old man when routine tests revealed hypouricemia . In the second case , a 76 -year -old woman , hypouricemia was also a fortuitous discovery . She had major xanthinuria and a radiotranslucid lithiasis in the right kidney .Hereditary xanthinuria is characterized by hypouricemia , low urinary urate excretion and increased concentration of xanthine and to a lesser extent hypoxanthine . The disease results from a defect in xanthine oxidase and is considered to be transmitted by autosomal recessive heredity . This rare metabolic disorder is more often asymptomatic and detected by routine chemistry . Development of xanthine lithiasis is directly related to the low solubility of xanthine and is the main complication of the disease , occurring in 30 -40 % of patients . There is no effective treatment and the only useful measure is to prevent xanthine urolithiasis by maintaining urinary output above 2 l /day .