A 78-year-old man presents with a 2-month history of fever and intermittent abdominal pain. He develops peritoneal signs and at laparotomy is found to have an area of infarcted bowel. Biopsy shows inflammation of small-to medium-sized muscular arteries.

The patient has classic polyarteritis nodosa. It is a multisystem necrotizing medium-size vessel vasculitis that, prior to the use of steroids and cyclophosphamide, was uniformly fatal. Patients commonly present with signs of vascular insufficiency in the involved organs. Abdominal involvement is common. In 30% of patients, antecedent hepatitis B virus infection can be demonstrated; immune complexes containing the virus have been found and are likely pathogenic.Small-vessel vasculitides include granulomatosis with polyangiitis (Wegener), microscopic polyangiitis, the Churg-Strauss syndrome, Henoch-Schonlein purpura, and cryoglobulinemic vasculitis. Granulomatosis with polyangiitis usually involves the sinuses, lungs, and kidneys. Chest x- ray may reveal cavities, infiltrates, or nodules. Many patients also develop glomerulonephritis which may result in acute renal failure. On biopsy, the vasculitis is necrotizing and granulomatous. Microscopic polyangiitis is a multisystem necrotizing vasculitis that typically results in glomerulonephritis, pulmonary hemorrhage, and fever. Lung biopsy shows inflammation of capillaries. Patients may also have mononeuritis multiplex and palpable purpura. Classic polyarteritis nodosa rarely involves the lungs.