Question

Syphilitic aneurysm most commonly involves which part of the aorta?

• A. Arch of aorta
• B. Descending aorta
• C. Abdominal aorta above the renal arteries
• D. Abdominal aorta below the renal arteries

Hint:

Think thoracic aorta, the elastic segment fed by vasa vasorum hit by endarteritis.

Answer 1

The Correct Option is A

Step 1: Syphilitic (luetic) aneurysm is a complication of tertiary syphilis. The treponemal endarteritis obliterans affects the vasa vasorum of the aortic wall, causing ischaemic destruction of the media. This weakens the wall and leads to aneurysm formation.

Step 2: The thoracic aorta is the predominant site because its media is richest in elastic tissue and is supplied by abundant vasa vasorum, which is the exact target of the obliterative endarteritis. Within the thoracic aorta the ascending segment is affected most often (about 50 percent), then the arch (about 35 percent), then the descending thoracic aorta (about 15 percent).

Step 3: Among the four listed options, the arch of the aorta is the only thoracic site, so it is the correct answer. The descending aorta is involved much less commonly, and the abdominal aorta (above or below the renal arteries) is the classic site for atherosclerotic aneurysm, not syphilitic aneurysm.

Step 4: Therefore syphilitic aneurysm characteristically involves the thoracic aorta, and from the given choices the arch of the aorta is the answer.