[The 493th case: recurrent edema of bilateral lower extremeties]

A 43-year-old male patient with onset of edema caused by nephrotic proteinuria and low titer of anti-M type phospholipase-A₂-receptor (PLA₂R) antibody was diagnosed as idiopathic membranous nephropathy by renal biopsy. Administrated with prednisone 40 mg once a day and cyclosporine 100 mg twice a day as front-line regimen, the patient relapsed after transient partial remission. When treatment was combined with cyclophosphamide 100 mg once a day, the 24-hour total urine protein and titer of anti-PLA₂R antibody were even elevated. Therefore, the patient received rituximab 1 g intravenously in April 2019, October 2019 and October 2020 respectively. CD19 positive B lymphocytes in peripheral blood were eliminated from 71/μl to zero. Immunosuppressants and corticosteroids were withdrawn successively. On the last follow-up in November 2020, the anti-PLA₂R antibody was negative, and the 24-hour total urine protein and serum albumin was 4.4 g and 34 g/L, respectively. This case suggested the potential efficacy of rituximab for refractory membranous nephropathy. Further studies should explore whether the titer of anti-PLA₂R antibody indicates the dose of rituximab.