[Update: polyarteritis nodosa]

Polyarteritis nodosa (PAN) is a necrotizing arteritis of medium-sized vessels, which is often fatal if untreated. It frequently affects the skin (nodules and ulcers), the peripheral nervous system (mononeuritis multiplex) and the visceral vessels (stenoses and microaneurysms). The complex diagnostic work-up requires discriminating PAN from infectious, malignant, drug-induced and other inflammatory conditions. It can be subclassified into further variants (idiopathic, associated with hepatitis B, associated with hereditary inflammatory diseases or isolated cutaneous disease). While idiopathic and hereditary inflammatory variants require immunosuppressive treatment, the hepatitis B-associated variant is treated with virustatic agents and plasmapheresis. The isolated cutaneous variant has a good prognosis and rarely requires highly potent immunosuppressives.