A 58-year-old man with untreated tertiary syphilis develops a thoracic aortic aneurysm. At autopsy the intimal surface shows longitudinal wrinkles resembling tree bark, and the aneurysm involves the ascending aorta while the abdominal aorta is spared. What histological change underlies this pattern of involvement?

• A Atheromatous destruction of the intima extending into the outer media
• B Transmural granulomatous inflammation destroying the adventitia
• C Cystic degeneration of elastic fibers in the middle third of the media
• D Obliterative endarteritis of the vasa vasorum with medial ischemic damage ✓

Explanation

Treponema pallidum infects the vasa vasorum of the aorta, producing obliterative endarteritis with plasma cell-rich perivascular infiltrates. Ischemic death of medial smooth muscle and elastic tissue then causes dilation and scarring of the intima, giving the tree bark look. The vasa vasorum are richest in the ascending arch, so the thoracic segment is affected and the abdominal aorta is characteristically spared, unlike atherosclerotic aneurysms.

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.