Hereditary Angioedema — MFDS Part 1 MCQ

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HardHuman DiseaseHereditary AngioedemaMFDS Part 1

A 23-year-old woman develops progressive, non-pruritic swelling of her lips following a dental extraction. She reports previous episodes of hand swelling and severe, self-limiting abdominal pain, without urticaria. Her father has experienced similar attacks, and her serum C4 concentration is low between episodes. Deficient functional activity of which protein best explains this presentation?

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Correct answer: A — C1 esterase inhibitor

The correct answer is A, C1 esterase inhibitor. Recurrent non-pruritic angioedema without urticaria, episodic abdominal pain, an autosomal dominant family history and low C4 indicate classic hereditary angioedema caused by deficient C1 esterase inhibitor activity. Type I results from reduced protein concentration, whereas type II involves a dysfunctional protein. Inadequate inhibition of kallikrein and factor XIIa causes excess bradykinin, increased vascular permeability and oedema; dental procedures can precipitate attacks. Factor VIII deficiency causes haemophilia A, and von Willebrand factor deficiency causes mucocutaneous bleeding. Protein C deficiency predisposes to venous thrombosis. Fibrinogen deficiency principally produces a bleeding disorder rather than recurrent angioedema.

Reference: Electronic Medicines Compendium, Icatibant 30 mg solution for injection in pre-filled syringe, SmPC section 5.1 Mechanism of action, current UK SmPC (last updated 4 July 2022), https://www.medicines.org.uk/emc/product/13867/smpc