Long-term kidney and patient outcomes in pure versus mixed lupus membranous nephritis.

Objective: Pure membranous lupus nephritis [pMLN, Class V International Society of Nephrology/Renal Pathology Society (ISN/RPS)] is traditionally considered less aggressive than mixed forms of MLN (mMLN, Classes III/IV ± V ISN/RPS). Only two trials have compared the outcome of these two forms of MLN, with inconclusive results. In this retrospective multicentre study, we assessed and compared the short and long-term outcomes of pMLN versus mMLN. Methods: Patients diagnosed with pMLN or mMLN on their first kidney biopsy were included. The main outcomes were complete renal response after 1 year, sustained complete response, relapse rates, chronic kidney disease (CKD)-free survival, and the composite outcome of kidney failure (KF)/death-free survival. Results: Of the 195 patients included, 96 (49.2%) pMLN had milder immunological features of active LN at baseline compared to 99 (50.8%) with mMLN. At kidney biopsy, the National Institute of Health activity and chronicity indices were lower in patients with pMLN ( Conclusion: This study challenges the long-standing view of pMLN as a generally benign condition, suggesting that less intensive treatment of pure MLN may have contributed to less favourable hard outcomes in the long-term.