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: Recall the pathogenesis. In late-stage syphilis, spirochaetes trigger an obliterative endarteritis of the vasa vasorum. Loss of blood supply to the medial layer produces patchy medial necrosis and scarring, classically described as tree-bark wrinkling of the intima.

Step 2: Sites with the most elastic media and the densest vasa vasorum are hit hardest, and that is the thoracic aorta. The proximal thoracic segments bear the brunt: ascending aorta first, arch next, then descending thoracic aorta.

Step 3: Map this onto the choices. Descending aorta is a thoracic site but far less common than the arch. The two abdominal options point toward atherosclerotic disease rather than a luetic process, so they can be excluded.

Step 4: The single best thoracic answer offered is the arch of the aorta.

\[\boxed{\text{Arch of aorta}}\]