Polyarteritis nodosa (PAN) is a rare form of systemic necrotizing vasculitis that primarily affects small and medium-sized arteries without glomerulonephritis or vasculitis in the arterioles, capillaries, or venules.

In the United States the incidence of PAN is 3:100,000 to 4.5:100,000 per year. Internationally the incidence is 1.8:100,000 to 6.3:100,000 per year, except in populations with endemic hepatitis B, where the incidence of PAN can reach 7.7:100,000. There is no observed racial predilection, and males are more frequently affected by a ratio of 1.6:1. The onset usually occurs between 40 and 60 years of age.

An immune response is the suspected cause of PAN. About 30% of patients with PAN test positive for the hepatitis B surface antigen. The hepatitis B antigen aggregates with circulating hepatitis B antibodies in the serum and produces vascular lesions.