Segmental mediolytic arteritis--electronmicroscopic and immunohistochemical study.

We examined specimens of human gastroepiploic artery aneurysm from a patient having several visceral aneurysms using electronmicroscopic and immunohistochemical techniques. The histopathological and ultrastructural findings confirmed the diagnosis of segmental mediolytic arteritis. Arterial smooth muscle cells from the gastroepiploic artery contained cytoplasmic vacuoles, media was thin and the internal elastic membrane showed distortion. X-ray microanalysis revealed calcium deposits in the medial extracellular space. Antigenic determinants of human immunoglobulins, fibrinogen, complement C3a and factor VIII were demonstrated in the injured artery wall, suggesting that immunocomplexes deposited in the artery wall may be associated with local injury. These findings support the role of autoimmune disorders in the pathogenesis of segmental mediolytic arteritis.