Hereditary Angioedema — RACP Adult Medicine MCQ

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ModerateGeneral Internal MedicineHereditary AngioedemaRACP Adult Medicine

A 30-year-old woman presents with episodic angioedema without urticaria affecting her face and extremities. She has a family history of similar episodes. Her C4 level is persistently low even between attacks. C1-inhibitor level is low. What is the diagnosis?

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Correct answer: B — Acquired C1-inhibitor deficiency

Hereditary angioedema type I is characterised by recurrent angioedema WITHOUT urticaria, low C4 (even between attacks – useful screening test), and low C1-inhibitor level and function. It is autosomal dominant. Acute attacks are treated with C1-inhibitor concentrate (Berinert), icatibant (bradykinin B2 receptor antagonist), or fresh frozen plasma. Long-term prophylaxis includes C1-inhibitor replacement, lanadelumab (anti-kallikrein), or berotralstat. Adrenaline and antihistamines are INEFFECTIVE as the mechanism is bradykinin-mediated, not histamine-mediated.

Reference: eTG – 2025 – Immunology; ASCIA – 2024 – HAE Guidelines