A 58-year-old man with untreated syphilis in the past develops a slowly expanding mass in the chest. CT shows an aneurysm of the ascending aorta with dense intimal calcification that spares the abdominal aorta. Chest radiograph shows vertical calcification lines resembling the bark of a tree. Which structure was damaged by the causative organism to produce this aneurysm?

• A Vasa vasorum of the adventitia ✓
• B Intimal endothelium of the aorta
• C Valvular commissures only
• D Periaortic lymphatics

Explanation

Treponema pallidum causes obliterative endarteritis of the vasa vasorum, producing ischemic destruction of the aortic media with loss of elastic fibers and scarring. The weakened media dilates, giving an ascending aortic aneurysm classically with a tree-bark intima and calcification that characteristically stops before the diaphragm. The best distractor, valvular commissural involvement, explains the accompanying aortic regurgitation but not the aneurysm itself.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.