Hereditary xanthinuria in 2 Pakistani sisters: asymptomatic in one with beta-thalassemia but causing xanthine stone, obstructive uropathy and hypertension in the other.

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We describe a 3 -year -old Pakistani girl who presented with recurrent urinary infections . She had a nonfunctioning hydronephrotic right kidney and hypertension . At operation a calculus was impacted in the right ureter with dilatation of the pelviocaliceal system . Nephrectomy was performed . Histology revealed end stage pyelonephritis . The calculus consisted of pure xanthine . Further investigations demonstrated low serum uric acid and absent urinary uric acid with increased excretion of xanthine . Eight months after nephrectomy blood pressure had decreased to normal . Her 5 -year -old sister , who has beta-thalassemia , also has a low serum uric acid concentration and xanthinuria . The treatment of choice is to increase fluid intake so that the urine xanthine concentration remains below the level at which xanthine crystallizes . This may require adjustment of the urine pH .