[Infections and vasculitis].

Vasculitides are rare diseases characterized by inflammation of blood vessels. According to diameter of the blood vessels involved in the inflammatory process, the clinical presentation and the histological appearance, different vasculitic syndromes may be distinguished. Primary vasculitides are of unknown origin while secondary vasculitides may be caused by drugs, malignancy or infection. Panarteriitis nodosa caused by chronic Hepatitis B and mixed cryoglobulinemia secondary to chronic Hepatitis C are classical examples of vasculitides triggered by infections. However, these are rare complications of chronic viral hepatitis. Patients infected by HIV frequently suffer from vasculitis, which may be caused by opportunistic infections and by defects in immune regulation. In numerous case reports, various other infectious particles have been reported to cause different forms of vasculitis, either by direct infection of endothelial cells or by induction of an immunologic process leading to blood vessel destruction. Immunologically mediated vasculitis secondary to infection may be due to a predisposing reactivity of the patient's immune system. After successful treatment of the infection, the vasculitis usually subsides. Therefore, all patients with vasculitis should be evaluated for underlying infection.