Polyarteritis nodosa

Polyarteritis nodosa (PAN) is a rare vasculitis affecting middle-sized arteries. Its annual incidence in Europe is estimated to range between 0 and 1.6 cases per million, while the prevalence is about 31 cases per million. The frequency of hepatitis B virus (HBV)-related PAN has declined in developed countries since vaccination against HBV has been implemented. Specifically, before vaccination against HBV was implemented on a large scale, more than one-third of adults with PAN were infected by HBV, whereas currently only 5 % of European adults with PAN are infected by HBV. PAN is usually considered an immune-complex-driven vasculitis. However, the evidence of abundant CD4+ T cells in vascular inflammatory infiltrates suggests that PAN may also be induced by a T-cell response. Clinically, PAN usually presents with constitutional manifestations as well as symptoms and signs related to the organs affected. Organ ischemia is thought to be due to vascular stenoses, while ruptured aneurysms can result in tissue hemorrhage. The most frequent clinical features include constitutional manifestations, myalgia, arthralgia, peripheral neuropathy and mononeuritis multiplex. There are no specific blood tests to diagnose PAN, but inflammatory markers are typically elevated. Therefore, the diagnosis rests on histological changes in affected organs, showing a transmural vessel wall infiltrate, or angiographic findings, including small saccular or fusiform aneurysms and stenoses. Treatment includes glucocorticoids in patients without poor prognostic factors or cyclophosphamide if the disease is life- or organ-threatening.