Southwestern Internal Medicine Conference: vasculitis--it's time to reclassify.

Based on the lack of knowledge of pathophysiologic mechanisms, there has not been a clear and consistent classification of vasculitides. During the past few years, our understanding of these disorders has been enhanced by an appreciation of the role of anti-neutrophil cytoplasmic antibodies. These antibodies exist in two types, a c-ANCA, which corresponds to anti-proteinase 3 antibodies, and a p-ANCA, which corresponds mostly with anti-myeloperoxidase antibodies. Treatment has improved prognosis markedly in these diseases. Most patients can be successfully treated with combinations of treatments including steroids, pulse steroids, cytotoxic agents, and plasmapheresis. Based on antineutrophil cytoplasmic antibodies and response to treatment, a classification is proposed. This classification includes all necrotizing crescentic glomerulonephritis as vasculitis. The vasculitides are divided according to whether they involve large arteries, medium arteries, or small vessels, which include arterioles, capillaries, and venules. Small vessel vasculitides frequently are associated with necrotizing crescentic glomerulonephritis and are divided into three categories: ANCA-associated, anti-GBM associated, and immune complex-associated. Renal biopsy is extremely useful in providing pathologic confirmation of small vessel vasculitis.