A 7-year-old boy develops urticaria, angioedema, and wheezing within 5 minutes of eating peanuts. The immediate phase of this reaction is primarily mediated by which preformed mast cell granule mediator?

• A Leukotriene C4
• B Prostaglandin D2
• C Tryptase
• D Histamine ✓

Explanation

In Type I hypersensitivity, preformed histamine released from mast cell granules causes the immediate phase (within minutes): vasodilation, increased vascular permeability, smooth muscle contraction, and mucus secretion. Leukotrienes and prostaglandins are newly synthesized lipid mediators responsible for the late-phase reaction (2-24 hours). Tryptase is a mast cell marker measured to confirm anaphylaxis but is not the primary effector of immediate symptoms.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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