We report on a girl who was diagnosed with classical hereditary xanthinuria due to an incidental finding of extremely low Levels of uric acid in the blood. The girl is compLetely asymptomatic. Hereditary xanthinuria is a rare autosomal recessive disease that usually causes early urolithiasis but may cause rheumatoid arthritis-like disease and even be associated with defects in the formation of bone, hair and teeth. In Israel it has mostly been described in patients of Bedouin origin. Throughout the world, only about 150 cases have been described; about two thirds of these patients were asymptomatic. Since the clinical presentation and age of symptom appearance are diverse, the case raises questions as to the required follow-up of these patients and as to whether a low oxalate diet should be initiated.