Systemic vasculitic syndromes.

The current lack of knowledge about the factors underlying both the etiopathogenesis and extent of the clinical expression of necrotizing vasculitis is illustrated by recent articles. "Benign" vasculitis may present as localized disease in skin, gut, or even muscle; but on long-term follow-up, systemic involvement frequently occurs. Exciting studies on the occurrence of viruses such as hepatitis C in vasculitis compound these problems, because they are associated with multiple syndromes and the mechanism underlying their relationship to vasculitis remains to be elucidated. Further subdivision of antineutrophil cytoplasmic antibodies may aid in classification, but currently, their association with disease activity and extent obscures that role. Age is also less useful, because Kawasaki syndrome may occur rarely in adults and polyarteritis nodosa was reported in a large series of children. Differentiation is important because of the various responses to therapy. The first controlled study of cyclophosphamide as therapy for necrotizing vasculitis confirms its early benefit but, interestingly, shows no difference in 10-year survival rates. The addition of plasma exchange is of benefit only in the small number of patients with severe renal involvement who are dialysis-dependent at onset.