Histopathological classification of pauci-immune glomerulonephritis and its impact on outcome

Rapidly progressive renal failure is a common but severe feature of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis. A histopathological classification for ANCA-associated pauci-immune glomerulonephritis was developed for prognostication of these patients. The present study aims to classify patients of pauci-immune glomerulonephritis according to this classification and its impact on outcome. Eighty-six subjects with pauci-immune glomerulonephritis between July 2006 and October 2012 were included in the study. Their renal biopsies were reviewed and classified into focal, crescentic, sclerotic and mixed class as per the new classification. The outcomes were analyzed after 6 months of treatment. Of the 86 subjects, 34 (39.53 %) were granulomatosis with polyangiitis, 36 (41.86 %) microscopic polyangiitis, 1 eosinophilic granulomatosis with polyangiitis, while the rest (17.44 %) were unclassifiable. Thirteen (15.5 %), 43 (51.2 %), 12 (14.3 %) and 16 (19 %) patients were classified as focal, crescentic, sclerotic and mixed class, respectively. The mean serum creatinine at baseline was 280.23, 659.46, 573.72 and 542.78 µmol/L in focal, crescentic, sclerotic and mixed class, respectively. The probability of improvement in renal functions at 6 months decreased from focal to crescentic to mixed to sclerotic class, while the probability of death was highest in the sclerotic class followed by the mixed class. This difference in outcome was maintained irrespective of the clinical diagnosis or the Birmingham Vasculitis Activity Score. Our study has shown that the histopathological classification can be used to predict the severity of renal dysfunction as well as the treatment outcomes in pauci-immune glomerulonephritis.