RESUMO
The deficiency of enzyme hypoxanthine-guanine phosphoribosyltransferase(HPRT) results in hyperuricemia and subsequently manifests in diverse symptoms. Lesch-Nyhan syndrome is a disorder characterized by hyperuricemia, mental retardation, choreoathetosis, spasticity and self-mutilation, resulting from complete deficiency of the enzyme, whereas partial deficiency of the enzyme shows symptoms of milder forms more often without abnormal neurologic signs. A 7-year-old boy with normal growth and psychomotor development presented with a uric acid stone accompanied by a disproportionate increase of serum/urine uric acid level. The stone was removed by nephrolithotomy and further enzymatic study on lysed erythrocytes showed less than 1% of the normal HPRT activity. After initiation of treatment with allopurinol, the uric acid level was rapidly decreased to a normal range and the patient has not shown hyperuricemia or nephropathy since. Although partial HPRT deficiency is not commonly seen, this possibility should be considered whenever urolithiasis is accompanied by disproportionately high levels of serum uric acid.