Minimal change disease induced by tiopronin: a rare case report and a review of the literature

Tiopronin (TP), a glycine derivative with a free thiol, is extensively used for the treatment of cystinuria. Moreover, TP is usually prescribed as hepatoprotective medicine in China. In the present case, a 36-year-old female who presented with foamy urine and general edema was admitted to the hospital. She had been taking TP for six months to treat drug-induced liver injury due to anti-tuberculosis drugs including isoniazid, rifampicin and pyrazinamide. The urine tests at admission revealed nephritic-range proteinuria with a daily urinary protein level of 8,024 mg. Meanwhile, albumin and cholesterol levels were abnormal. The light microscopy was negative and electron microscopy showed foot process effacement. Thus, minimal change disease (MCD) was diagnosed, and TP was consequently discontinued. Finally, the patient accomplished complete remission within five weeks after the cessation of TP without undergoing glucocorticoid therapy. TP was speculated to play an antigenic role in this adverse effect. To date, there are only two similar cases documented in the literature. Herein, we first report a case of a Chinese patient who generated MCD after prolonged TP administration. Clinicians should be wary of the occurrence of MCD due to TP when administering long-term therapy of TP. A weekly urinalysis may be useful for early identification of TP-induced MCD.