Comparison of Lupus Nephritis Onset Before and After Age 50: Impact on Presentation and Outcomes in an Inception Cohort.

OBJECTIVE Renal involvement in systemic lupus erythematosus (SLE) most commonly occurs in women of the reproductive age group. However, it may theoretically start at any age. In this study, We aimed to explore the impact of lupus nephritis (LN) stratified by age of onset, with a cutoff at 50 years, on clinical presentation and disease outcomes. METHODS We included 246 inception cohort patients who developed LN during follow-up. We classified patients based on the age of LN onset into Group 1 (before age 50; 205 patients) and Group 2 (≥50, late-onset LN [LoLN]; 41 patients). Outcomes included complete proteinuria recovery (CPR) at one year, an adverse composite outcome (end-stage renal disease [ESRD], a sustained ≥40% eGFR decline, or death), subsequent LN flares, and any increase in non-renal SLICC damage index (SDI). The association with outcomes was studied using Cox proportional hazards model. RESULTS At baseline, the median [IQR] age was 31.4 [25.2, 38.5] years for Group 1 and 58.4 [53.9, 64.5] years for Group 2 (p<0.01). Group 2 (LoLN) patients had a higher median creatinine level (p=0.03), lower median eGFR (p<0.01) and proteinuria levels (p=0.01), and lower median SLEDAI-2K score (p=0.04). In the Cox models, there were no significant differences between the two groups in terms of achieving CPR or developing the adverse composite outcome. However, LoLN was associated with higher odds of any increase in non-renal SDI and showed a trend for fewer subsequent flares. CONCLUSION LoLN is not associated with significant differences in short- or long-term renal outcomes.