RESUMEN
Cystinuria is an autosomal recessive defect in transepithelial transport of dibasic amino acids (e.g. cystine) which involves the proximal canaliculi, small intestine and central nervous system. It is the least common cause of nephrolithiasis, accounting for 1 to 3% of renal calculi. The natural course of the disease, characterised by recurrent stone formation, can frequently lead to renal failure, if left untreated. Until recently, treatment of cystinuria has been limited to symptomatic management including intensive hydration and urine alkalinisation. Different drugs that react with cystine to form soluble complexes have been used but their efficacy remains questionable. We present the case of a 6-year-old boy with severe, recurrent cystine urolithiasis treated with captopril. The diagnosis of cystine urolithiasis was established after a 3-year course of clinically apparent nephrolithiasis, characterised by stone passage. At the age of 5 years he underwent lithotripsy and nephrolithotomy for removal of staghorn calculi. Since then treatment with citrate and magnesium supplementation combined with captopril was introduced. After a follow-up of 12 months the patient remained stone-free. Urinary cystine decreased from 230 to 136 mg per gram creatinine. We conclude that captopril can be useful in the treatment of cystine urolithiasis in children.