An abdominal aortic aneurysm in a 70-year-old man is found to measure 5.5 cm. Which pathological process is MOST responsible for its development?
- A Atherosclerosis-related destruction of medial elastin and smooth muscle by matrix metalloproteinases ✓
- B Cystic medial necrosis with collagen replacement of elastin
- C Syphilitic endarteritis obliterans of vasa vasorum causing adventitial fibrosis
- D Autoimmune IgG4-related aortitis
Correct answer: A. Atherosclerosis-related destruction of medial elastin and smooth muscle by matrix metalloproteinases
Explanation
Abdominal aortic aneurysms are predominantly atherosclerotic; the mechanism involves chronic inflammatory infiltration (macrophages, T cells), overexpression of matrix metalloproteinases (especially MMP-9 and MMP-2), and destruction of medial elastin and smooth muscle, leading to wall weakening and dilation. Cystic medial necrosis causes thoracic aortic aneurysms (Marfan syndrome, bicuspid aortic valve). Syphilitic aortitis causes thoracic (ascending) aneurysms via vasa vasorum endarteritis.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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