Leiden classification of ANCA-associated glomerulonephritis

Antineutrophil cytoplasmic antibody (ANCA)-associated glomerulonephritis is the morphological correlate of renal involvement in small vessel vasculitis, such as microscopic polyangiitis or granulomatous polyangiitis. The extent of glomerular changes that initially present as necrosis of glomerular capillaries with reactive proliferation of Bowman's epithelia (so-called crescents) followed by scarring of the glomeruli and the relevance for the clinical prognosis have been evaluated by a group of pathologists and nephrologists led by the nephropathology in Leiden. The retrospective analysis of kidney biopsies and clinical data published in 2010 resulted in the assignment of histological changes to four categories (focal, crescentic, sclerosing and mixed). These classes correlate with the estimated glomerular filtration rate (eGFR) as independent renal parameters at disease onset and after 1 and 5 years. The data show that the sclerosing class had the worst and the focal variant the best prognosis. The Leiden classification of ANCA-associated glomerulonephritis thus represents a prognostically relevant classification of glomerular changes in ANCA-associated vasculitis. Only future validation studies will show whether this classification is generally applicable as a basis for treatment decisions and will become widely introduced into clinical practice.© Springer-Verlag Berlin Heidelberg 2013.