There are a number of autoimmune disorders that can produce aortitis. These noninfectious inflammatory processes include many of the connective tissue diseases such as rheumatoid arthritis, ankylosing spondylitis, Reiter's syndrome, giant cell arteritis, Behcet's disease, and relapsing polychondritis. These diseases weaken the aortic wall and predispose to aneurysm formation with a predilection for involvement of the ascending aorta (Fig. 13). The most common noninfectious cause of aortitis is Takayasu's arteritis, usually seen in young Asian women. This is a vasculitis of unknown etiology that primarily affects the thoracic aortic arch with variable involvement of the abdominal aorta and pulmonary arteries. This disease produces inflammation of the media and adventitia that most commonly results in arterial stenosis and occlusion, hence the use of the descriptor ''pulseless'' disease. Aneurysmal dilatation of the aorta is a less common manifestation of the disease .
Patients with thoracic aneurysms resulting from the aortitis associated with connective tissue disease usually have fusiform dilatation of the ascending aorta with variable involvement of the aortic valve annulus. Fine curvilinear calcification may be seen in the wall of the aneurysm. The CT features of Takayasu's arteritis of the aorta have been described . Unenhanced CT demonstrates high attenuation of the thickened aortic wall and mural calcifications in the majority of affected patients. Mural enhancement during the arterial phase following contrast administration was seen in 75% of patients with active disease and was 100% specific. Aortic arch and branch vessel stenoses are present in the majority of patients. Aneurysm formation is uncommon, may be fusiform or saccular in shape, and is often difficult to distinguish from dilatation proximal to a hemodynamically significant stenosis.
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