A medical student develops diffuse erythema and mild edema of the shoulders after spending an afternoon in strong sunlight. Studies of such injured skin show that endothelial leakage begins several hours after exposure and persists for many hours. Which mechanism of increased vascular permeability best accounts for this pattern?

• A Histamine-induced endothelial cell contraction in postcapillary venules
• B Transcytosis of fluid through VEGF-stimulated vesiculovacuolar channels
• C Leukocyte-mediated endothelial injury at adherent neutrophil contacts
• D Direct endothelial injury producing delayed-prolonged leakage from capillaries and venules ✓

Explanation

Delayed-prolonged leakage follows mild to moderate injury such as sunburn or thermal burns: edema appears 2 to 12 hours after injury and persists for hours to days, reflecting direct damage to endothelium of capillaries and venules together with delayed effects of the mild injury itself. Histamine causes the immediate-transient response beginning within minutes, and leukocyte-mediated and VEGF-driven leakage describe other, temporally distinct mechanisms.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.