Resorption of immune deposits in membranous lupus nephritis following rituximab vs conventional immunosuppressive treatment.

OBJECTIVES

Studies on repeat renal biopsies in membranous LN (MLN) are limited, and evaluation of treatment response is mainly based on proteinuria. EM of renal biopsies from rituximab (RTX)-treated MLN patients has revealed resorption of sub-epithelial ICs. Whether resorption phenomena are useful for treatment evaluation, or differs between treatment regimens is not known. We studied EM findings and clinical treatment response in MLN patients after RTX vs conventional immunosuppressive treatment.

METHODS

Twenty-four patients with MLN and renal biopsies performed before and after treatment were included in this retrospective observational study. Laboratory data were collected at both biopsy occasions. Seven patients had received RTX and 17 had received conventional treatment (CYC, MMF or AZA). Electron micrographs of renal tissue were scored using an arbitrary scale (0-3) for the level of sub-epithelial ICs, resorption of ICs and podocyte fusion.

RESULTS

Sub-epithelial ICs decreased after treatment, however not significantly and with no difference between treatments. The resorption phenomena increased after RTX (P = 0.028), but not after conventional therapy (P = 0.29). Six out of seven (86%) RTX-treated patients had increased resorption vs 7/17 (41%) after conventional therapies (P = 0.047). Clinical responders had more pronounced resorption of ICs vs non-responders (P = 0.022).

CONCLUSIONS

We report increased resorption of ICs in repeat renal biopsies in MLN, especially after RTX treatment. Increased resorption phenomena were associated with clinical response, suggesting that EM findings may be useful for treatment evaluation in MLN. Although of limited size, the study indicates that RTX is effective both clinically and at a tissue level.