Polyarteritis nodosa.

Polyarteritis nodosa (PAN) is a systemic disease, but variants are cutaneous PAN and single-organ disease. Histologic confirmation of vasculitis in medium-sized arteries is desirable, and biopsies should be obtained from the symptomatic and least invasive sites. Angiography can show multiple microaneurysms in the viscera. Treatment includes high-dose corticosteroids, which are combined with immunosuppressive agents when internal organs are involved and with life-threatening disease. Once remission is achieved, maintenance agents are initiated. PAN is becoming a rare disease. International collaborative efforts are under way to establish better diagnostic and classification for all vasculitides, including PAN.