[Classification and index of necrotizing vasculitis].

The diagnosis of necrotizing vasculitis rests on histology which shows parietal fibrinoid necrosis, vascular and perivascular infiltrates and intraluminal thrombosis in varying degrees of association. However, histopathological classifications of necrotizing vasculitis according to the size of the diseased vessels or the appearance of vascular infiltrates are not satisfactory, since microvasculitis may successively to simultaneously involve vessels of different calibers and result (generally in succession) in leukoclastic or lymphocytic vasculitis. For this reason we give preference to an aetiological classification which includes five major entities, some of which were described over a century ago (periarteritis nodosa, Churg-Strauss syndrome, Wegener's disease, rheumatoid purpura and Mac Duffie syndrome); drug-induced vasculitis, infective vasculitis, vasculitis associated with blood diseases; vasculitis of connective tissue diseases; vasculitis that may accompany some system diseases (e.g. Kawasaki disease and Cogan's syndrome); and vasculitis that may complicate cryoglobulinaemia or congenital deficiencies in complement fraction or in alpha-1 antitrypsin. It can be seen that this is not the ideal classification, since the same causative agent may be found in several chapters (e.g. HB virus in periarteritis nodosa, infective vasculitis and cryoglobulinaemia). We describe in detail only those types of vasculitis which are not treated in other in this issue of the Revue du Praticien, notably Wegener's disease, Mac Duffie syndrome and Kawasaki disease.