[Xanthinuria with xanthine lithiasis in a patient with Lesch-Nyhan syndrome under allopurinol therapy]

It is the intention of this report to identify appropriate analytical tests which allow for the monitoring of allopurinol treatment of patients with Lesch-Nyhan syndrome and the prevention of uric acid or xanthine lithiasis.

A 12 year old boy with Lesch-Nyhan syndrome presented with signs of compulsive automutilation, motoric and mental retardation and cerebral palsy. Paraclinical patient showed hyperuricemia and significant hyperuricosuria. During administration of allopurinol (200 mg/d) he developed fever, an urinary tract infection and dilatation of pelviureteric junction which was suspected of being nephrolithiasis. During hospitalisation, the purine metabolism was intensively monitored. The allopurinol treatment was adjusted according to clinical and laboratory data.

The renal scanning diagnostic showed the develepment of a functionally impaired left kidney. Later this kidney had no part in tubulo-secretorical function. It was necessary to remove surgical two renal stones. The composition of the stones was exclusively xanthine. Serum concentration and urinary excretion of xanthine and hypoxanthine were massively enlarged. The elimination of uric acid in urine was normal. But subsequently, the left kidney had to be removed despite intensive care.

Lesch-Nyhan syndrome is a disorder caused by congenital absence of the enzyme hypoxanthineguanine phosphoribosyltransferase and an increase of the enzyme activity of adenine phosphoribosyltransferase. Treatment should be adjusted to patient's age and weight. An adapt treatment with allopurinol and optimal fluid intake reduce the risk of uric acid or xanthine lithiasis. Laboratory monitoring includes testings for serum concentration and urinary excretion of uric acid, xanthine and hypoxanthine. Sole a normal concentration of uric acid is not sufficient for therapy control. Assessment of the urine sediment by microscopy or infrared spectroscopy will enable early detection of uric acid or xanthine lithiasis.