Histopathological atlas of renal diseases: ANCA-associated vasculitis (first part).

"ANCA-associated vasculitis" are Wegener's Granulomatosis, Micropolyarteritis and its renal-limited variant (previously called idiopathic necrotizing glomerulonephritis). According to the "Chapel Hill Consensus Conference" classification, ANCA-associated vasculitis are characterized by prevalent involvement of small-size vessels, whereas medium and large-size arteries involvement is the marker of Polyarteritis Nodosa. But the vessel size-based classification is not always powerful enough, because also in ANCA-associated vasculitis the involvement of medium and large-size arteries if frequent. The distinctive marker of ANCA-associated renal vasculitis has therefore become the presence of necrotizing extracapillary glomerulonephritis, that is always absent in Polyarteritis Nodosa.