Vasculitides.

Polyarteritis nodosa (PAN) primarily affects mediumsized arteries that supply the skin, gut, nerve, and kidney, but may involve multiple organs.Microaneurysms of arteries to or within the kidneys, liver, or gastrointestinal tract are highly characteristic of PAN.Polyarteritis nodosa is not associated with antineutrophil cytoplasmic antibodies (ANCA) directed against either proteinase-3 or myeloperoxidase.Mononeuritis multiplex, an asymmetric sensory and motor neuropathy due to ischemia and infarction of peripheral nerves, occurs frequently in PAN.In mononeuritis multiplex, nerve conduction studies of peripheral nerves reveal a distal, asymmetric, axonal neuropathy involving both motor and sensory nerves.Polyarteritis nodosa is characterized pathologically by patchy, transmural inflammation in medium- and small-sized muscular arteries, sparing large arteries, capillaries, and the venous system. The inflammation leads to fibrinoid necrosis, but is not associated with granulomatous features.High-dose glucocorticoids are the mainstay of therapy in PAN. In cases that are rapidly progressive or life- or organ-threatening, however, cyclophosphamide is added to glucocorticoid treatment.Most cases of idiopathic PAN do not recur once a sound remission has been achieved with 6 to 12 months of therapy.■ A minority of PAN cases (now >10%) are associated with acute hepatitis B infection. Cases associated with hepatitis B are treated with regimens emphasizing antiviral therapy and only short courses of immunosuppression and plasmapheresis. [ABSTRACT FROM AUTHOR]