Hereditary Angioedema — SCE Dermatology MCQ

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ModerateInflammatory DermatosesHereditary AngioedemaSCE Dermatology

A 30-year-old woman presents with recurrent angioedema without urticaria affecting her face and lips. She has a family history of similar episodes. Complement studies show low C4 and low C1 esterase inhibitor level. What is the most likely diagnosis?

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Correct answer: A — Hereditary angioedema type I

Hereditary angioedema (HAE) type I (85% of cases) is characterised by low C1 esterase inhibitor levels AND low C4. Type II has normal levels but dysfunctional C1 inhibitor (low C4, normal C1-INH level, low functional assay). HAE presents with recurrent episodes of angioedema without urticaria, affecting the face, extremities, GI tract (causing abdominal pain), and potentially the larynx (life-threatening). It is autosomal dominant (SERPING1 mutation). C4 is low both during and between attacks, making it a useful screening test. Acute treatment includes C1 inhibitor concentrate, Icatibant (bradykinin B2 receptor antagonist), or Ecallantide.

Reference: BAD 2019; BSACI 2017 HAE Guidelines