A 35-year-old woman of Asian descent presents with blood pressure difference between arms, diminished left brachial pulse, and elevated ESR. MRI angiography shows segmental stenosis and wall thickening of the aortic arch and its main branches. This large-vessel vasculitis affects which layer of the arterial wall as the primary site of inflammation?
- A Intima (endothelial injury initiating the response)
- B Adventitia (vasa vasorum and adventitial granulomatous inflammation) ✓
- C Media (smooth muscle cell apoptosis by cytotoxic T cells)
- D All layers equally (transmural inflammation)
Explanation
Takayasu arteritis begins in the adventitia at the level of the vasa vasorum (the microvascular supply within the adventitia of large vessels). The inflammatory process is characterized by adventitial granulomatous inflammation with Langhans giant cells and lymphocytic infiltration that begins around the vasa vasorum, then extends inward through the media, causing smooth muscle necrosis and eventual fibrosis, with late intimal thickening causing stenosis. This 'outside-in' pattern differs from giant cell arteritis, which also involves the adventitia but more prominently affects the internal elastic lamina-media junction. The adventitial initiation explains the pattern of skip lesions in Takayasu.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
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Written and medically reviewed by the StethoPrep medical team.