โ ๏ธ Untreated HAE patients may experience attacks every 1โ2 weeks, each lasting 3โ4 days.
๐ About
- ๐ Incidence ~1 in 50,000 individuals.
- ๐งฌ Inherited angio-oedema, distinct from allergic/IgE-mediated causes.
๐งฌ Aetiology
- Autosomal dominant mutation in C1 esterase inhibitor (C1-INH) gene.
- โฌ๏ธ Leads to deficiency/dysfunction of C1-INH.
- โ Causes excessive bradykinin โ vascular permeability โ angioedema.
- ~25% of cases are due to new spontaneous mutations.
๐ฉบ Clinical Presentation
- โฑ๏ธ Attacks triggered by stress, surgery, trauma, infections, hormones, or foods.
- ๐ถ Typically presents in teenage years (though earlier in some).
- ๐ฎ Swelling of face, lips, tongue, pharynx, larynx โ risk of airway obstruction.
- ๐ด Red, non-urticarial rash (often mistaken for allergy).
- ๐ค Colicky abdominal pain from GI mucosal oedema (may mimic surgical abdomen).
๐ฌ Investigations
- โฌ๏ธ C1-INH plasma levels/function โ diagnostic marker.
- ๐งฌ Genetic testing confirms mutation in C1-INH gene.
- ๐งช C4 complement levels are usually persistently low.
๐ Management
- ๐จ Emergency care: ABC protocol, airway management, oxygen & fluids.
- ๐ Icatibant: Bradykinin receptor antagonist โ shortens attacks.
- ๐ C1-INH concentrate: For acute attacks & prophylaxis.
- ๐ Ecallantide (Kalbitor): Kallikrein inhibitor โ blocks bradykinin production.
- ๐ฉธ Fresh Frozen Plasma (FFP): Emergency replacement if C1-INH not available.
- ๐ Danazol / Stanozolol: Androgens โ โ hepatic C1-INH synthesis.
- ๐ Tranexamic Acid: Antifibrinolytic; sometimes for prophylaxis.
๐ UK Exam Pearls
- ๐ Distinguish HAE from allergy: swelling is not histamine-mediated, so antihistamines/steroids are ineffective.
- ๐ฌ๐ง NICE recommends icatibant or C1-INH concentrate for acute attacks in the UK.
- ๐ฉโโ๏ธ Always anticipate airway compromise โ early anaesthetic/ENT involvement if laryngeal oedema suspected.
- ๐ Clue in exams: recurrent abdominal pain + angioedema without urticaria.
- ๐งช Low C4 levels during and between attacks are a useful screening test.