Clinical and histological features of lupus nephritis in Japan: A cross-sectional analysis of the Japan Renal Biopsy Registry (J-RBR)

Aim: The clinical and histological features of lupus nephritis (LN) are highly variable, depending on race and ethnicity. The Japan Renal Biopsy Registry (J-RBR) is a nationwide registry of renal biopsies. Here, we report a cross-sectional analysis of Japanese LN using the J-RBR database. Methods: Out of 18 463 patients registered in the J-RBR, 331 LN patients, who received renal biopsy for the first time, were extracted and their clinical features were analyzed according to the ISN/RPS 2003 classification. Results: The median age of the 331 LN patients was 37 years (women, 81.3%). The frequencies of each of the ISN/RPS Classes were as follows: I, 1.2%; II, 7.9%; III (±V), 25.1%; IV-S (±V), 13.0%; IV-G (±V), 31.1%; V, 20.8%; and VI, 0.9%. The level of proteinuria and the prevalence of nephrotic syndrome were highest for Class IV-G (±V). When Classes I, II, and VI were excluded from the analysis, Class IV-G (±V) was significantly associated with a lower eGFR and severer haematuria than the other classes. Conclusion: This nationwide study revealed that Class IV-G (±V) was the most prevalent form of LN in Japan and was associated with a severe clinical renal presentation.