Objective: Membranous LN (MLN) is thought to have a more benign course than proliferative LN (PLN). We aimed to determine the differences in short- and long-term outcomes between patients with MLN and PLN.

Methods: We included patients with first biopsy-proven MLN and PLN. Short-term outcomes included complete proteinuria recovery (CPR), complete renal response (CRR) and primary efficacy renal response (PERR). Long-term outcomes included a sustained ≥40% reduction in baseline estimated glomerular filtration rate, end-stage kidney disease (ESKD), cardiovascular (CV) events, ≥2 increase in SLICC/ACR Damage Index and death. Univariable and multivariable Cox proportional hazard models were used to examine the effect of baseline characteristics on long-term outcomes.

Results: Of 215 patients, 51 had pure MLN and 164 had PLN. We found no significant differences between the two groups in achieving CPR, CRR and PERR at 1 and 2 years. Median time to outcomes was slightly, but insignificantly, longer in the MLN group. For long-term outcomes, PLN was associated with worse renal and non-renal outcomes, but this was not statistically significant. In the multivariable Cox proportional hazard models, ESKD was associated with the following baseline variables: younger age [hazard ratio (HR) 0.92, 95% confidence interval (CI) 0.87-0.97], higher creatinine (HR 1.01, 95% CI 1.01-1.02), low complement (HR 4.0, 95% CI 1.04-11.10) and higher chronicity index (HR 1.28, 95% CI 1.08-1.51).

Conclusions: The resolution of proteinuria in LN is slow. MLN is not a benign disease and may be associated with deterioration of renal function, ESKD, damage, CV events and death.