Mizoribine oral pulse therapy for steroid-dependent nephrotic syndrome

There have been reports of the use of mizoribine (MZB) oral pulse therapy for the treatment of systemic lupus erythematosus. We report its efficacy in a 9-year-old girl with steroid- and cyclosporine-dependent nephrotic syndrome (NS). The patient experienced relapses of NS when prednisolone was tapered to 20 mg/day after discontinuing cyclosporine due to biopsy proven toxicity. When methylprednisolone pulse therapy combined with prednisolone therapy (40 mg/day) failed to result in a complete remission after 3 weeks, oral MZB pulse therapy (total dose of 500 mg, 10 mg/kg per day in three divided daily doses twice a week) was given. This therapy was continued for 9 months and resulted in complete remission of the NS for 6 months despite the discontinuation of prednisolone. The serum concentration of MZB was above 2.5 μg/ml for about 10 h (from 3 h after the first dose of MZB to 2 h after the final dose). Thus, our results suggest that this regimen may be effective for patients with steroid-dependent NS.