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The 2003 International Society of Nephrology/Renal Pathology Society (ISN/RPS) system for classifying patients with lupus nephritis was based on glomerular lesions exclusively, despite the fact that lupus nephritis affects all compartments of the kidney. Hence, we analyzed the tubulointerstitial lesions in patients with lupus nephritis within the different classes and subclasses of the 2003 ISN/RPS system. Among 313 patients from five centers in northern China with lupus nephritis, interstitial inflammatory cell infiltration, tubular atrophy, and interstitial fibrosis were severe in 170 patients with class IV, moderate in 55 with class III, and mild in 19 with class II and in 69 with class V disease, each with significance. The severity of tubulointerstitial lesions in classes IV-segmental and III was similar, whereas the score of interstitial inflammatory cell infiltration in patients with subclass IV-global was significantly higher than that in those with subclass IV-segmental. Interstitial fibrosis and tubular atrophy were each significantly more prominent in patients with both active and chronic lesions than in those with active lesions alone. The correlation coefficient ranged from 0.222 to 0.811 comparing glomerular and tubulointerstitial indices. In multivariate Cox hazard analysis of tubulointerstitial lesions, indices of interstitial infiltration, tubular atrophy, and interstitial fibrosis were confirmed as significant independent risk factors for renal outcome. Thus, we found that the 2003 ISN/RPS classification system of lupus nephritis, based on glomerular lesions, could also reflect related tubulointerstitial lesions. Hence, we suggest that the extent of tubulointerstitial lesions may be helpful in predicting renal outcome in patients with lupus nephritis.

The 2003 International Society of Nephrology/Renal Pathology Society (ISN/RPS) pathological classification system of lupus nephritis specified the importance of vascular damage and indicated this should be included in the diagnostic summary. Few pathological studies of lupus nephritis, however, focus on the patterns of renal vascular involvement. Here we assessed renal vascular lesions in lupus nephritis based on the 2003 ISN/RPS classification system and evaluated their association with clinical and pathological data in a large cohort from a single center in China. Among 341 patients with lupus nephritis, 279 were diagnosed with single or multiple renal vascular lesions that included 253 with vascular immune complex deposits, 82 with atherosclerosis, 60 with thrombotic microangiopathy, 13 with noninflammatory necrotizing vasculopathy, and 2 with true renal vasculitis. Patients with thrombotic microangiopathy had the poorest renal outcome. In multivariate Cox hazard analysis after inclusion of renal vascular lesions, the new chronicity index score became a significantly better independent risk factor for renal outcome (hazard ratio 2.32). Thus, renal vascular lesions are common in lupus nephritis and closely correlate with clinical disease activity and renal outcome. Inclusion of a detailed description of renal vascular lesions in the ISN/RPS classification of lupus nephritis may strengthen its predictive value for renal outcome.