A 65-year-old man with a pulsatile abdominal mass has CT showing a 5.5 cm infrarenal aortic aneurysm with mural thrombus. The pathological process underlying most abdominal aortic aneurysms is:
- A Atherosclerosis causing intimal plaque with loss of medial smooth muscle and proteolytic matrix degradation ✓
- B Cystic medial necrosis with elastic lamina fragmentation
- C Adventitial inflammation with ischemic compromise of vasa vasorum leading to medial atrophy
- D Type III collagen deficiency causing fragile vessel walls
Correct answer: A. Atherosclerosis causing intimal plaque with loss of medial smooth muscle and proteolytic matrix degradation
Explanation
Abdominal aortic aneurysms are predominantly atherosclerosis-related; the atherosclerotic plaque compromises nutrient diffusion to the media, and local macrophage/MMP (matrix metalloproteinase) activity degrades medial elastin and collagen, weakening the wall. Cystic medial necrosis underlies thoracic aneurysms in Marfan syndrome; tertiary syphilis causes aneurysm via adventitial obliterative endarteritis of vasa vasorum; type III collagen deficiency causes Ehlers-Danlos type IV.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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