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) detectable on angiography. There are no specific serological markers and diagnosis depends on clinical presentation, angiography and tissue biopsy. Treatment with corticosteroid and immunosuppressive drugs is usually effective but PAN can pursue a relapsing course. Kawasaki disease affects children, usually under the age of 5 years, and presents as an acute, febrile exanthematous disease. Inflammation and damage of muscular arteries particularly affect the coronary arteries leading to aneurysm formation. Prompt diagnosis and treatment with aspirin and intravenous immunoglobulin have reduced the frequency of this complication. Relapse is rare although vascular damage results in an increased risk of cardiovascular disease later in life. Medium-sized vessels can also be involved in organ-limited vasculitis affecting the skin (cutaneous polyarteritis), gut or brain. Additionally, medium-sized vessels can be involved in vasculitic syndromes defined by the predominant involvement of microscopic or large vessels.