Medium vessel vasculitis

Polyarteritis nodosa (PAN) and Kawasaki's 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 tissue biopsy. Exclusion of hepatitis B infection is important. Treatment with corticosteroids and immunosuppressive drugs is usually effective, but PAN can pursue a relapsing course. Kawasaki's 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 reduces the frequency of these complications. Relapse is rare, although vascular damage results in an increased longer term risk of cardiovascular disease.