Vasculitis in primary vasculitides, granulomatoses, and connective tissue diseases.

Problems with the classification and diagnosis of vasculitides are discussed. The evidence related to the pathogenetic importance of immune complexes in vasculitis, both in experimental models and human disease, is reviewed. The finding, by immunofluorescence, of immunoglobulins and complement components in vessel walls has provided indirect evidence of a role of immune complexes in certain forms of human vasculitis. However, specific antigens have been demonstrated in very few instances, notably in some patients with hepatitis B infection. In most forms of human vasculitis there is no information about causative factors. The widely held belief that therapeutic drugs cause an appreciable proportion of cases of human vasculitis appears unfounded.