Conditions associated with xanthine stones:
(1) hereditary defect in xanthine oxidase (very rare autosomal defect)
(2) history of therapy with high doses of allopurinol
(3) Lesch-Nyhan syndrome (hereditary defect in purine metabolism)
(4) recent chemotherapy for malignant disease
Clinical findings:
(1) family history of stone disease (in the hereditary form)
Imaging studies:
(1) stones are radiolucent
(2) ultrasonography shows a stone with high density and a typical echo pattern
Laboratory findings:
(1) marked decrease in serum and urine uric acid
(2) elevated xanthine and/or hypoxanthine concentrations in the urine
(3) crystals in the urine, which may be confused with uric acid
(4) xanthine identified in stone analysis
Prevention:
(1) hydration all through the day and night to maintain a dilute urine
(2) ovo-lacto-vegetarian diet to increase the urine pH (alkalinize)
(3) reduced purine intake in diet
