Hereditary Angio-Oedema
⚠️ Untreated HAE patients may experience attacks every 1–2 weeks, each lasting 3–4 days.
📖 About
- 🌍 Incidence ~1 in 50,000 individuals.
- 🧬 Inherited angio-oedema, distinct from allergic/IgE-mediated causes.
🧬 Aetiology
- Autosomal dominant mutation in C1 esterase inhibitor (C1-INH) gene.
- ⬇️ Leads to deficiency/dysfunction of C1-INH.
- ❗ Causes excessive bradykinin → vascular permeability → angioedema.
- ~25% of cases are due to new spontaneous mutations.
🩺 Clinical Presentation
- ⏱️ Attacks triggered by stress, surgery, trauma, infections, hormones, or foods.
- 👶 Typically presents in teenage years (though earlier in some).
- 😮 Swelling of face, lips, tongue, pharynx, larynx → risk of airway obstruction.
- 🔴 Red, non-urticarial rash (often mistaken for allergy).
- 🤕 Colicky abdominal pain from GI mucosal oedema (may mimic surgical abdomen).
🔬 Investigations
- ⬇️ C1-INH plasma levels/function – diagnostic marker.
- 🧬 Genetic testing confirms mutation in C1-INH gene.
- 🧪 C4 complement levels are usually persistently low.
💊 Management
- 🚨 Emergency care: ABC protocol, airway management, oxygen & fluids.
- 💉 Icatibant: Bradykinin receptor antagonist → shortens attacks.
- 💉 C1-INH concentrate: For acute attacks & prophylaxis.
- 💉 Ecallantide (Kalbitor): Kallikrein inhibitor → blocks bradykinin production.
- 🩸 Fresh Frozen Plasma (FFP): Emergency replacement if C1-INH not available.
- 💊 Danazol / Stanozolol: Androgens → ↑ hepatic C1-INH synthesis.
- 💊 Tranexamic Acid: Antifibrinolytic; sometimes for prophylaxis.
📌 UK Exam Pearls
- 🛑 Distinguish HAE from allergy: swelling is not histamine-mediated, so antihistamines/steroids are ineffective.
- 🇬🇧 NICE recommends icatibant or C1-INH concentrate for acute attacks in the UK.
- 👩⚕️ Always anticipate airway compromise → early anaesthetic/ENT involvement if laryngeal oedema suspected.
- 🔍 Clue in exams: recurrent abdominal pain + angioedema without urticaria.
- 🧪 Low C4 levels during and between attacks are a useful screening test.
