Background While lupus nephritis (LN) is more common with higher severity and mortality in children than in adult-onset disease, data regarding long-term outcome of childhood-onset LN is rare.

Methods Long-term renal outcome and their treatment were assessed in 57 Korean childhood-onset LN patients diagnosed between 1999 and 2020 from a tertiary single center in Korea.

Results Median age at diagnosis of LN was 14.5 (range 7.8–17.8) years. Median follow-up period was 135 (30–266) months. 26.3% (15/57) of patients progressed to chronic kidney disease (CKD) stage 3–5 (CKD stage 3: 6 patients, stage 4: 1 patient, stage 5: 8 patients). 10-year renal survival was 100% in patients diagnosed after 2011, compared to 80.3% in patients diagnosed before 2011 (p=0.049). Comparing the two eras, there were no clear difference between the laboratory finding at diagnosis, the drug used, and the cumulative dose of cyclophosphamide or hydroxychloroquine, except that primary renal response rate was higher at the latter era (55.2% vs 82.1%, p=0.029), and the diagnosis age was slightly younger in the earlier era (median 13.5 vs 14.6, p=0.056). Hydroxychloroquine use was significantly associated with maintaining renal estimated glomerular filtration rate (eGFR) higher than 60ml/min/m2 at 10 years (95.2% vs 77.2%), and 20 years (68.6% vs 16.1%), respectively (p= 0.033).

Conclusions Early diagnosis and timely adequate treatment, and the use of hydroxychloroquine are important in the long-term kidney prognosis of childhood-onset LN.