In Canada, hereditary Angioedema is managed by allergy & immunologists. Hereditary angioedema (HAE) is a rare autosomal-dominant disease that produces unpredictable attacks of non-itchy, non-urticarial swelling of the skin, abdominal wall, larynx, and oropharynx, driven by uncontrolled bradykinin generation rather than histamine. Prevalence is approximately 1 in 50,000 worldwide (Bygum 2009), and over 90% of cases are caused by deficient (type 1) or dysfunctional (type 2) C1-esterase inhibitor (C1-INH).
Hereditary angioedema (ICD-10: D84.1, hereditary deficiency of complement component C1 inhibitor) is a bradykinin-mediated swelling disorder caused by inherited dysfunction or deficiency of C1-esterase inhibitor (C1-INH) — a serine protease inhibitor (serpin) encoded by SERPING1 that regulates the classical complement, contact, fibrinolytic, and coagulation pathways. Three classic phenotypes are recognized. HAE type 1 (85% of cases) features low antigenic and functional C1-INH from missense, nonsense, or splicing variants in SERPING1. HAE type 2 (15%) features normal antigenic but reduced functional C1-INH from mutations that produce a dysfunctional protein, typically at the reactive-center loop.
The key symptoms of Hereditary Angioedema are: Recurrent attacks of non-pitting, non-itchy subcutaneous swelling of the hands, feet, face, genitals, or limbs that build over 12-36 hours and resolve over 2-5 days without treatment., Severe colicky abdominal pain with nausea, vomiting, and watery diarrhea from bowel-wall edema, often mimicking surgical abdomen — a frequent cause of unnecessary appendectomy or laparotomy before diagnosis., Laryngeal edema with throat tightness, hoarseness, dysphagia, stridor, and progressive airway obstruction — accounts for most pre-treatment deaths., A flat, serpiginous, non-pruritic skin rash (erythema marginatum) preceding 25-50% of attacks by hours to a day., Tingling, tightness, or fullness in the affected area as a prodrome 4-24 hours before visible swelling., Triggers identifiable in 60-70% of attacks — minor trauma (dental work, intubation, surgery), psychological stress, infections, menstruation, hormonal contraceptives or hormone replacement therapy, ACE inhibitors, and some antibiotics., Mood symptoms (irritability, fatigue, low mood) commonly preceding an attack, particularly in adolescents..
Diagnosis is biochemical and depends on three blood tests in the right clinical setting: serum C4, antigenic C1-INH, and functional C1-INH. In HAE type 1, both antigenic and functional C1-INH are below the lower limit of normal and C4 is low. In HAE type 2, antigenic C1-INH is normal or elevated but functional C1-INH is low and C4 is low. C4 alone is approximately 88-92% sensitive and 96% specific when measured outside an attack; sensitivity exceeds 98% during an attack. Acquired angioedema (AAE) shares low C4, low C1-INH function, and low antigenic C1-INH but classically also low C1q (versus normal C1q in hereditary disease). HAE with normal C1-INH (HAE-nC1INH) shows normal C4 and C1-INH testing; the diagnosis combines a strong clinical picture (recurrent bradykinin-pattern angioedema, family history, lack of response to antihistamines and steroids) with genetic testing for F12, PLG, KNG1, and other recognized genes. WAO/EAACI 2021 guidelines recommend confirmatory testing twice at least 4 weeks apart. Genetic testing is offered when the diagnosis remains uncertain, before family screening, or for HAE-nC1INH. Differential diagnosis includes mast-cell-mediated allergic angioedema (acute onset, often with urticaria, responsive to adrenaline), ACE inhibitor angioedema (clinically similar but acquired and reversible with drug withdrawal), and idiopathic histaminergic angioedema. Imaging is rarely required; abdominal CT during an attack shows characteristic bowel-wall edema with ascites that resolves within days.
Modern targeted therapy has transformed HAE outlook. Pre-1980s case series reported mortality from laryngeal asphyxiation in 25-30% of untreated patients; post-2010 cohorts on consistent on-demand therapy and long-term prophylaxis show mortality close to general-population rates. The HELP, COMPACT, and APeX-2 trials each demonstrated attack-rate reductions of 44-95% with modern prophylactic agents, and over 70% of patients on lanadelumab achieve a 12-month attack-free interval. Quality-of-life scores rise substantially: AE-QoL scores improve by 20-30 points on prophylaxis in trial data. Childbearing is generally safe with planning and pdC1-INH support. Major unmet needs include diagnostic delay, equitable access in low- and middle-income countries, and HAE with normal C1-INH, where biomarkers and trial evidence remain limited.
Care should be coordinated through an allergy and immunology specialist with HAE expertise, ideally at a designated comprehensive care center. Specialists handle confirmatory testing, family cascade screening, individualized prophylaxis selection, pregnancy planning, dental and surgical pre-medication, and access to expensive targeted therapies.
Find specialists →An acute attack treated early with on-demand C1-INH, icatibant, or ecallantide begins to improve within 30-90 minutes and fully resolves within 4-24 hours. Untreated attacks last 2-5 days. Long-term prophylaxis reaches steady-state attack reduction within 4-8 weeks of starting subcutaneous C1-INH, lanadelumab, or berotralstat. Quality of life typically improves within 3-6 months of effective prophylaxis.
Regular moderate exercise is encouraged and does not provoke attacks for most patients. Avoid contact sports that involve repeated facial trauma if attacks are frequent. Pre-treat with on-demand therapy before high-risk activities in particularly trigger-sensitive patients. Stress-management approaches (CBT, mindfulness) reduce psychological triggers in observational studies.
Look for an allergist or immunologist who is part of a HAE comprehensive care center (US HAEA Angioedema Center of Excellence or equivalent international designation), follows at least 10 HAE patients, and has 24-hour access to on-demand therapy. Pediatric HAE warrants a pediatric allergist with HAE experience and an established airway plan.
Medically reviewed by AIHealz Medical Editorial Board · May 13, 2026
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