Syphilitic aortitis. Light micrograph of a section through the wall of the inflamed aorta of a patient with syphilis. In the tertiary stage of syphilis, a sexually transmitted bacterial infection, the blood vessels become inflamed. The vessels which supply the aorta are compromised thereby restricting blood flow to the aortic wall. The aortic wall weakens and scars, and may bulge outwards under the pressure of arterial blood, to form an aortic aneurysm (swelling). This can rupture, which can result in heavy internal bleeding and may be fatal.