Cutaneous polyarteritis nodosa.

The term polyarteritis nodosa (PAN) presently includes classic systemic PAN, cutaneous PAN, and microscopic PAN (microscopic polyangeiitis). Cutaneous PAN involves the deep dermis and the panniculus, with anatomopathological findings diagnostic for arteritis. The most frequent clinical manifestation of cutaneous PAN is the presence of nodules on the lower legs, which frequently are found at different stages of development. At times, they may not leave residual changes, but generally a violaceous livedoid color or pigmentation with retiform appearance persists for months and even years. Ulceration also is a frequent complication of cutaneous PAN. Pain, arthralgias, malaise, and moderate fever are frequently associated symptoms. Histopathologically, cutaneous PAN shows a single artery involved with diagnostic inflammatory changes. The involved artery is always located in the deep dermis or in the panniculus. Inflammatory active skin nodules show a necrotizing arteritis with variable amounts of fibrinoid necrosis and leukocytoclasia, edema and inflammatory cells. The presence of focal panniculitis surrounding the involved artery is characteristic, in contrast with the more diffuse panniculitis usually found in other nodular diseases. Cutaneous PAN has a variable course, with repeated exacerbations. Salicilates relieve the pain in most instances and may be the only treatment required to improve the symptoms in patients with moderate flare-ups. A short course of corticosteroids therapy at a moderate dose is the most effective treatment to relieve the symptoms and to reduce the inflammation. Patients with an increased ASO titer should always be treated with penicillin.