Tiopronin-nephropathy in a female adolescent patient with cystinuria

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Herein, we report the case of an adolescent patient with nephrotic-range proteinuria and hypoproteinemia caused by tiopronin. The patient was a 13-year-old adolescent girl who had been diagnosed with cystinuria at the age of 9-years. Initial treatment comprised urinary alkalization and tiopronin. Urinalysis showed 3+ proteinuria 43 months after the initiation of tiopronin treatment. Proteinuria was accompanied by 2.2 g/dL of hypoalbuminemia, hyperlipidemia, and high adiponectin levels. Considering the adverse effects of tiopronin, it was immediately withdrawn. Ten days after withdrawal of the drug, proteinuria and hypoproteinemia had completely resolved, and steroid therapy was therefore not required. These findings are consistent with those of nephrotic syndrome secondary to medication in our patient. Tiopronin, which is a common treatment for cystinuria, may cause nephrotic-range proteinuria and hypoproteinemia. Therefore, periodic urine analyses and patient follow-ups are warranted during tiopronin therapy for cystinuria.