Xanthinuria type I is a rare autosomal recessive disorder of purine metabolism that is characterized by excess levels of xanthine and presence of xanthine stones in the urine, leading to renal function deterioration. Surveys suggest a population incidence of 1 in 6,000 to 1 in 69,000, most reported cases are from Mediterranean and Middle Eastern countries.
Xanthinuria, Type I results from a deficiency of the the xanthine dehydrogenase (XDH), an enzyme that normally catalyzes the terminal two steps of the purine degredation pathway: the formation of xanthine from hypoxanthine and uric acid from xanthine, the normal end-product of purine metabolism.