Antineutrophil cytoplasmic antibodies in the classification of vasculitis.

Two important types of antineutrophil cytoplasmic antibodies (ANCA) have been identified: anti-proteinase 3 and anti-myeloperoxidase antibodies. In the appropriate clinical setting, the presence of either is virtually diagnostic of the subset of vasculitis that includes Wegener's granulomatosis, microscopic polyangiitis (microscopic polyarteritis), the Churg-Strauss syndrome, idiopathic pauci-immune necrotizing and crescentic glomerulonephritis, and related and overlapping forms of these vasculitidies. The finding of ANCA throughout this group identifies these syndromes as belonging to a single category or spectrum of disease.