Vasculitis associated with primary rheumatologic diseases.

Vasculitis is an uncommon but important manifestation of autoimmune rheumatic diseases. Although the blood vessels of any organ can be involved, cutaneous involvement of arterioles and venules is the most common. Autoimmune rheumatic diseases may present as systemic vasculitis, and systemic vasculitis may simulate autoimmune rheumatic diseases. A crucial event in the initiation, localization, and propagation of vascular injury involves activation of the vascular endothelium by a variety of stimuli, including cytokines, complement split products, and cognate interactions between endothelial and T cells. Endothelial cell permissiveness to the deposition of circulating immune complexes or in situ formation of immune complexes in the vessel wall is also important. Vascular injury may be mediated by local or systemic activation of the complement system as well as autoantibody or T-cell-dependent mechanisms. This review focuses on the clinical features and pathogenic mechanisms involved in vasculitis complicating autoimmune rheumatic diseases.