Does the time to the onset of lupus nephritis impact renal disease presentation and outcomes?

OBJECTIVES: Lupus nephritis (LN) most commonly develops in the initial years after Systemic Lupus Erythematosus (SLE) onset. We aimed to investigate the impact of the time to LN onset on the clinical presentation and outcomes of LN. METHODS: We included 246 inception cohort patients who developed LN during follow-up. We categorized patients into three groups based on the time to LN onset: group 1 (early, ≤1 year, 160 patients), group 2 (intermediate, >1 to ≤5 years, 42 patients), and group 3 (delayed, >5 years, 44 patients). The outcomes assessed were complete proteinuria recovery (CPR) at one year, the occurrence of an adverse composite outcome (end-stage kidney disease [ESKD], a sustained ≥40 % decline in eGFR, or death), and the development of subsequent LN flares. Cox proportional hazard models were used to study associations with the outcomes. RESULTS: At baseline, the median [IQR] age was 34.3 [26.2, 44.7] years, with a median disease duration of 0.6 [0.2, 2.6] years. Delayed LN patients were older at baseline, had higher SDI, used glucocorticoids and immunosuppressives less frequently, and were less likely to achieve CPR at 1 year. Early LN patients had the lowest risk of developing the adverse composite outcome. In the Cox models, compared to early LN, intermediate LN was associated with an increased risk of developing the adverse composite outcome and showed a trend towards a higher association with subsequent LN flares. CONCLUSIONS: Intermediate LN, occurring between the first and fifth year after SLE onset, is associated with the worst renal outcomes.