Background Renal relapse has known to be a poor prognostic factor of renal function impairment in patients with lupus nephritis (LN). However, there was few studies that identified the risk factors of renal relapse. Therefore, we conducted a study based on 35 years of experience at a single center to find predictors of renal relapse.

Methods Among 401 patients of LN treated at Seoul St. Mary’s hospital from 1985 to 2019, 296 patients who reached complete remission were enrolled. We retrospectively analyzed the clinical, laboratory, pathologic and therapeutic parameters. The timing and cumulative risk of renal relapse were identified by Kaplan-Meier methods. The independent risk factors for renal relapse were examined by Cox proportional hazards regression analyses.

Results The median follow-up time after the diagnosis of LN was 131 months. Renal relapse had occurred in 157 patients, and 139 patients maintained complete remission. Renal relapse had occurred in 38.2%, 57.6% and 69.2% of patients within 5-year, 10-year, and 20-year after achievement of complete remission, respectively. Age of onset of SLE and LN were significantly younger in patients with renal relapse (26.3 vs 29.7, p=0.006 and 28.1 vs 31.7, p=0.004, respectively), and the ratio of absence of immunosuppressive maintenance treatment was also higher (p=0.002) in patients with renal relapse. In Cox proportional hazards regression analyses, age at onset of LN (HR 0.987, p=0.016) and absence of immunosuppressive maintenance therapy (HR 1.819, p=0.004) were identified to independent risk factors of renal relapse.

Conclusions We found that LN onset at an earlier age and absence of immunosuppressive maintenance treatment independently predicted renal relapse in patients with LN who achieved complete remission.