Usefulness of ISN/RPS classification of lupus nephritis

About 50-80% of patients with lupus suffer from lupus nephritis which is one of major causes of morbidity and mortality. Renal pathologists and nephrologists should evaluate the degree of histological damages to establish therapeutic plans for lupus nephritis. In order to standardize definitions, to emphasize clinically relevant lesions, and to improve interobserver reproducibility, the International Society of Nephrology/Renal Pathology Society (ISN/RPS) classification was proposed. Recently, several retrospective validation studies concerning the utility of the ISN/RPS classification, especially among class IV, were performed. In these reports, reproducibility is improved by the definition of diagnostic term, but the outcome related with classification, especially in class IV, is controversial. We performed retrospective analysis of 99 biopsy-proven subjects with lupus nephritis in our facility using the ISN/RPS classification. The class IV-G group tended to exhibit a worse renal outcome, but the difference compared with IV-S was not significant. In a Cox proportional hazards models, Independent histological predictors of poor renal outcome were extracapillary proliferation, glomerular sclerosis and fibrous crescents, while hyaline thrombi and fibrous adhesions were of favorable renal outcome. Both were similarly observed in IV-G and IV-S. The more qualitative categorization by the response to standard treatment may be needed to emphasize clinically relevant lesion related to renal outcome.