Medium vessel vasculitis

Polyarteritis nodosa (PAN) and Kawasaki disease are primary systemic vasculitides with predominant medium-sized vessel involvement. PAN typically affects muscular arteries causing aneurysms (nodosa). There are no specific serological markers and diagnosis depends on clinical presentation, angiography and/or tissue biopsy. Primary systemic small vessel vasculitis with medium vessel involvement should be excluded. Hepatitis B-related PAN is now rare and should be distinguished as a ‘vasculitis with probable aetiology’. Similarly, monogenic diseases including deficiency of adenosine deaminase 2 that cause a PAN-like presentation are now being identified. Treatment of PAN with corticosteroid and immunosuppressive drugs is usually effective but a relapsing course is typical. Kawasaki disease affects children, usually under the age of 5 years, and presents as an acute, febrile exanthematous disease. Coronary artery involvement predominates and can lead to aneurysm formation and thrombosis. Prompt treatment with intravenous immunoglobulin and aspirin reduce the frequency of these complications. Relapse is rare, although vascular damage results in an increased longer term risk of cardiovascular disease.