A fair-skinned man develops marked erythema and blistering over his shoulders 6 hours after spending the afternoon at the beach. The leakage of fluid into the blister results from which pattern of increased vascular permeability?

• A Immediate sustained response mediated by mast cell histamine
• B Increased transcytosis across capillary endothelium
• C Retraction of endothelial cells in postcapillary venules
• D Delayed prolonged leakage due to direct endothelial injury ✓

Explanation

Sunburn is the classic example of direct endothelial injury producing delayed prolonged leakage: damage to all levels of the microcirculation begins 2 to 12 hours after the insult and persists for hours to days until vessels thrombose or repair. The histamine-driven venular gap response is immediate and short lived, so options A and C describe the wrong time course. Transcytosis via VEGF-induced channels contributes modestly but is not the dominant mechanism here.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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