[Xanthinuria type I as the cause of nephrolithiasis in 17-years old girl].

Classic xanthinuria is a rare metabolic defect concerning the final reactions of purine catabolism. There are two types of the disorder: type I results from xanthine dehydrogenase (XDH) deficiency, while type II is characterized by lack of both XDH and aldehyde oxidase activity. Both types are clinically similar and are characterized by elevated xanthine concentration in body fluids that can lead to xanthine crystallisation. The most common manifestation of the disease is urolithiasis, but in most cases xanthinuria remains asymptomatic and the diagnosis is accidental. In the paper we report the first case study of xanthinuria in Poland in a child presenting with urolithiasis. 17-years old female patient was diagnosed because of recurrent urinary lithiasis and hypouricemia was detected during routine tests. Plasma and urine concentrations of oxypurines were measured by high-performance liquid chromatography (HPLC) and showed typical features of xanthinuria: hypouricemia, hypouricosuria, xanthinuria and elevated plasma xanthine. The allopurinol loading test demonstrated type I xanthinuria. The presented case report supports that first symptoms of xanthinuria can appear at any age and this disorder should be considered during diagnosing urolithiasis.