Mesaortitis

MESAORTITIS, mesaortitis (from Greek mesos—middle and aortitis—inflammation of the aorta), inflammation of the middle layer of the aorta. The term mesaortitis is used to denote inflammation of the aortic wall in cases where inflammatory changes are localized predominantly (more rarely, exclusively) in the middle layer. Mesaortitis can be acute and chronic. Acute mesaortitis, expressed as purulent infiltration of the middle layer of the aorta with necrosis and destruction of it, complicated by the development of an acute aneurysm or perforation of the vessel wall, is sometimes observed in typhus, tonsillitis, and streptococcal sepsis (see Aorta). Chronic mesaortitis has the character of productive inflammation (mesaortitis productiva) and manifests along the course of the vasa vasorum of the middle layer in focal proliferation of lymphoid, plasma, and epithelioid cells; mesaortitis of this kind is rarely encountered in rheumatism and in sepsis lenta. Most often, chronic productive mesaortitis is observed in syphilis (mesaortitis productiva syphilitica), being the most frequent manifestation of visceral syphilis. Syphilitic mesaortitis affects mainly the thoracic aorta, very rarely extending to the abdominal aorta; relatively rarely it is expressed in the formation of true gummas in the aortic wall (mesaortitis gummosa). More often, it is a matter of the development of granulation foci along the course of the vasa vasorum (hence the old term "mesaortitis granulosa"), consisting of lymphoid and plasma cells; at the same time, there is a new formation of branches of the vasa vasorum, penetrating into the inner layers of the middle coat and into the inner coat. These newly formed vessels with infiltrates separate the elastic-muscular layers of the middle layer of the aorta and, by cutting and destroying them, disrupt their continuity. Sometimes, in addition to these infiltrates, small granulation foci of epithelioid cells are observed. Often, there is the presence of giant cells of the Langhans type among the infiltrates and granulation foci. In places of the greatest development of the indicated changes, necrosis of more or less extensive areas of the middle layer may occur. Of the other layers of the aortic wall in syphilitic mesaortitis, the adventitia is the most altered, in which, as a rule, one finds cuffs of infiltrates of lymphoid and plasma cells along the course of the vasa vasorum, as well as productive vasculitis. As for the inner coat, thickenings are observed in it corresponding to the places of greatest change in the middle layer due to compensatory nonspecific proliferation of connective tissue. The above-described kind of changes are characteristic of the more or less fresh period of syphilitic mesaortitis; subsequently, a gradual replacement of infiltrates, granulation foci, and necrosis with scar connective tissue occurs. In connection with this, in the late periods of syphilitic mesaortitis, the microscope reveals only focal scars, forming, as it were, bald spots in the middle coat, which are especially well visible when staining a section for elastic tissue. Macroscopically, syphilitic mesaortitis gives a very characteristic picture: the inner surface of the thoracic aorta, especially in its ascending part, has an uneven appearance in places or entirely due to the presence of a number of small depressions in the form of small scars or linear wrinkles. These wrinkles can branch or be distributed in a star-like manner, and are often arranged in rows, giving some places of the inner surface of the aorta a more or less uniformly wrinkled or shagreen appearance. Larger scars of the inner surface of the aorta are encountered more rarely. This picture, characteristic of syphilitic mesaortitis, can be obscured by the presence of significant compensatory thickening of the inner coat or the addition of banal atherosclerosis. Syphilitic mesaortitis is the most frequent cause of aortic aneurysms (see Aorta, Syphilitic aortitis).

A. Abrikosov. Lit.—see lit. to the art. Syphilitic aortitis.