Lupus nephritis at systemic lupus erythematosus onset and kidney outcomes in a Latin American biopsy-proven cohort.

BackgroundThe prognostic relevance of lupus nephritis (LN) occurring at systemic lupus erythematosus (SLE) onset versus later remains uncertain, particularly in Hispanic populations.MethodsWe conducted a retrospective cohort study of adults (≥18 years) with biopsy-proven LN from tertiary centers in Colombia (2011-2024). The exposure was LN at SLE onset (LNSO), defined as LN diagnosed concurrently with SLE or with kidney biopsy within 30 days of SLE onset, versus LN occurring later (non-LNSO). The primary outcome was end-stage kidney disease (ESKD), defined as sustained eGFR <15 mL/min/1.73 m2 for ≥3 months, chronic dialysis, or kidney transplantation. Secondary outcomes were all-cause mortality and a composite of ESKD, death, or doubling of creatinine. Associations were estimated using cause-specific Cox and Fine-Gray models. A 180-day landmark analysis assessed the impact of no remission at 6 months.ResultsAmong 428 patients, 281 (65.7%) had LNSO and 147 (34.3%) non-LNSO. Median follow-up was 5.3 years. ESKD occurred in 72 patients (16.8%) and did not differ by LNSO status (log-rank p = 0.278). LNSO was not associated with ESKD (adjusted HR 0.87; 95% CI 0.48-1.60) or in competing-risk models (sHR 0.85; 95% CI 0.19-3.84). Lower baseline eGFR, higher NIH chronicity index, and higher non-renal damage were associated with ESKD. The composite outcome occurred in 156 patients and was not associated with LNSO. No remission at 6 months strongly predicted adverse outcomes.ConclusionsLNSO was not independently associated with kidney or survival outcomes. Baseline function, chronicity, non-renal damage, and early response were the main prognostic factors.