A 65-year-old hypertensive man has a thoracic aortic aneurysm (TAA). Unlike abdominal aortic aneurysms (AAA), TAA in hypertensives most commonly results from:

• A Atherosclerosis destroying the media from the intima side
• B Cystic medial degeneration (medionecrosis) with loss of smooth muscle and elastic fibres ✓
• C Syphilitic aortitis with obliterative endarteritis of the vasa vasorum
• D Inflammatory AAA with periaortic fibrous tissue from immune-mediated destruction

Explanation

Hypertensive thoracic aortic aneurysms result primarily from cystic medial degeneration (CMD, also called Erdheim medionecrosis): loss of aortic smooth muscle cells and fragmentation and loss of elastic fibres in the media, replaced by pools of basophilic ground substance (myxoid material). This weakens the medial layer, allowing dilatation under systemic pressure. CMD is also the pathological basis of aneurysms in Marfan and Loeys-Dietz syndromes. Most AAAs are atherosclerotic in origin. Syphilitic aortitis targets the ascending aorta/arch via vasa vasorum obliteration. Inflammatory AAA is a perianeurysmal fibrosis variant of AAA.

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

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Written and medically reviewed by the StethoPrep medical team.