A 58-year-old hypertensive man started on lisinopril six weeks ago presents with sudden lip swelling and mild stridor. There is no urticaria and complement levels are normal. The chemical mediator responsible for this episode is:

• A Histamine released by IgE-sensitized mast cells
• B Bradykinin accumulating because of reduced degradation ✓
• C Leukotriene C4 from arachidonate 5-lipoxygenase activity
• D Thromboxane A2 from platelet cyclooxygenase activity

Explanation

ACE-inhibitor angioedema results from accumulation of bradykinin, since angiotensin-converting enzyme is identical to kininase II, the enzyme that degrades bradykinin. The absence of urticaria argues against a histamine-mediated allergic reaction, making antihistamines ineffective. Leukotriene C4 drives bronchoconstriction in asthma, and thromboxane A2 is a platelet aggregator, neither producing isolated mucosal edema in this manner.

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.