Also known as periarteritis nodosa, this is a rare but potentially serious disease, caused by a disturbance of the immune system (see IMMUNITY). Prolonged fever and obscure symptoms referable to any system of the body are associated with local areas of inflammation along the arteries, giving rise to nodules in their walls. Large doses of CORTICOSTEROIDS, coupled with IMMUNOSUPPRESSANT treatment, usually curtail the disorder. Recovery occurs in about 50 per cent of cases.