A patient with hereditary angioedema has recurrent episodes of subcutaneous and submucosal swelling without urticaria. The mediator responsible for the edema in this condition is:

• A Histamine released from mast cells
• B Bradykinin generated by uninhibited kallikrein due to C1-inhibitor deficiency ✓
• C IL-1 causing vascular permeability
• D Leukotriene C4 from arachidonic acid cascade

Explanation

Hereditary angioedema results from C1-inhibitor (C1-INH) deficiency. C1-INH normally inactivates plasma kallikrein; without it, kallikrein cleaves kininogen to produce excess bradykinin, which binds B2 receptors on endothelium to increase vascular permeability. The absence of urticaria distinguishes it from histamine-mediated angioedema. Treatment with icatibant (B2 antagonist) or C1-INH concentrate is effective.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.