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

Objective Renal involvement in systemic lupus erythematosus (SLE) most commonly occurs in women in the reproductive age group; however, it may theoretically start at any age. In this study, we aimed to explore the effect 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 (< 50 years; 205 patients) and group 2 (≥ 50 years, late-onset LN; 41 patients). Outcomes included complete proteinuria recovery (CPR) at 1 year, an adverse composite outcome (end-stage renal disease, a sustained ≥ 40% decline in estimated glomerular filtration rate [eGFR], or death), subsequent LN flares, and any increase in nonrenal Systemic Lupus International Collaborating Clinics/American College of Rheumatology Damage Index (SDI). The association with outcomes was studied using the Cox proportional hazards model. Results At baseline, the median age was 31.4 (IQR 25.2-38.5) years for group 1 and 58.4 (IQR 53.9-64.5) years for group 2 ( P < 0.01). Group 2 (late-onset LN) patients had a higher median creatinine level ( P = 0.03), lower median eGFR ( P < 0.01) and proteinuria levels ( P = 0.01), and a lower median SLE Disease Activity Index 2000 (SLEDAI-2K) score ( P = 0.04). In the Cox models, there were no significant differences between the 2 groups in terms of achieving CPR or developing the adverse composite outcome. However, late-onset LN was associated with higher odds of any increase in nonrenal SDI and showed a trend for fewer subsequent flares. Conclusion Late-onset LN is not associated with significant differences in short- or long-term renal outcomes.