Histological reclassification of lupus nephritis

This review examines the progress in clinico-pathologic studies following the publication of the International Society of Nephrology (ISN)/Renal Pathology Society (RPS) 2003 classification of lupus nephritis. Major features in this classification system include non-ambiguous diagnostic criteria based on quantitative assessment of histological abnormalities and further classification of Class IV lesions with regard to the predominance of segmental or global lesions.

The new classification has been applied in two recent retrospective studies. Key findings included improved diagnostic concordance compared with the World Health Organization classification for lupus nephritis, but no observable difference in renal outcome between Classes IV-S and IV-G during short-term follow up. The data also suggested that fibrinoid necrosis and interstitial inflammation may be more prominent in the IV-S group. While the new classification stipulates the description of individual lesions indicating activity or chronicity, it has not devised new composite histological scores. In this regard, recent studies on novel histological indices of lupus renal biopsies based on digital imaging and computerized data analysis have demonstrated a better correlation with clinical parameters.

The ISN/RPS 2003 classification facilitates accurate communication between pathologists and clinicians. It also provides a clear framework for standardization, upon which the clinical and pathogenetic significance of individual lesions and histological subtypes require further elucidation.