OBJECTIVE: To describe a case ofcystinuria treated with tiopronin that produced thenephrotic syndrome.METHODS/RESULTS: A case of nephrotic syndromewith ascites and heart failure in a patient who hadreceived tiopronin for the treatment of cystinuria ispresented. Cystinuria as a rare cause of kidney stones isanalyzed. The clinical features, diagnosis and the sideeffects of treatment with tiopronin are discussed. Thepatient recovered after withdrawal of the drug.CONCLUSIONS: It must be emphasized that patientstreated with tiopronin should be screened for proteinuria.