Localized vasculitis.

The mechanisms of vasculitis are poorly understood, but involve immune-mediated destruction of vessel walls. Depending on the syndrome, there is significant variability in the size and types of vessels involved, as well as the nature of the inflammatory infiltrate. In addition, there is a wide variation from 1 patient to another in the extent of involvement throughout the vascular tree. In some forms of vasculitis that are histologically indistinguishable from systemic syndromes, the inflammatory process appears to be isolated, or localized to a single site or organ. In most such cases, especially in localized forms of necrotizing polyarteritis, the prognosis is far better than for corresponding systemic vasculitides, and progression to systemic disease is unusual even without immunosuppressive treatment. However, for other types of vasculitic syndromes, especially Wegener's granulomatosis and antineutrophil cytoplasmic autoantibody-related vasculitis, presentation as a localized process warrants immediate treatment and may herald a prolonged, if relatively limited, disease. This article outlines the clinical and pathologic features of the vasculitis syndromes that may be localized at the time of diagnosis, and emphasizes which features are associated with progression to systemic disease.