Aortic lesion in Marfan syndrome: the ultrastructure of cystic medial degeneration.

Areas of medial alteration (Erdheim cystic medionecrosis) in an aortic root aneurysm surgically removed from a patient with Marfan syndrome were studied with an electron microscope. The single striking morphologic abnormality was the disorganized, haphazard architecture of the media in these areas. This lesion is interpreted as being an abortive reparative response to hemodynamic stress in a condition with a molecular defect in the structural proteins of connective tissue.