Angioedema — Med2Date

📋 Key Information Summary

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Angioedema is transient, localised swelling of deep dermis, subcutaneous tissue, or submucosa; laryngeal involvement is a medical emergency with risk of fatal asphyxiation.
Two principal pathophysiological pathways: histamine-mediated (allergic / mast-cell) and bradykinin-mediated (hereditary angioedema, ACE-inhibitor induced).
Histamine-mediated angioedema typically responds to adrenaline, H₁-antihistamines, and corticosteroids; bradykinin-mediated angioedema does not — misdiagnosis delays effective treatment.
Hereditary angioedema (HAE) is caused by C1-inhibitor deficiency (Type I ~85 %, Type II ~15 %); Type III (normal C1-INH) is rarer and often factor-XII mutation–related.
ACE-inhibitor angioedema accounts for 20–40 % of emergency angioedema presentations in Australia; onset may occur months to years after commencing therapy.
First-episode or diagnostic uncertainty requires C4 level as screening test — if low, proceed to C1-inhibitor quantitative and functional assays.
Emergency airway management takes precedence; early anaesthetic/ENT review if any stridor, voice change, or tongue swelling.
For histamine-mediated attacks: adrenaline 0.01 mg/kg IM (max 0.5 mg), IV dexchlorpheniramine or promethazine, hydrocortisone IV.
For HAE acute attacks: C1-inhibitor concentrate (Berinert®) IV or icatibant (Firazyr®) SC — both available through special-access pathways in Australia.
ACE inhibitors must be permanently discontinued after an angioedema episode; switch to ARB or alternative with monitoring.
All patients with confirmed HAE should carry a personalised action plan and medical-alert identification; consider long-term prophylaxis with danazol, tranexamic acid, or subcutaneous C1-INH (Haegarda®).
Aboriginal and Torres Strait Islander peoples may face delayed presentation due to geographic remoteness; ensure culturally safe follow-up and access to adrenaline autoinjectors.

Introduction & Australian Epidemiology

Angioedema is characterised by transient, localised subcutaneous or submucosal swelling resulting from increased vascular permeability in deep tissue layers. Unlike urticaria, which affects superficial dermis, angioedema involves deeper structures and presents with non-pitting, asymmetrical swelling — most commonly of the lips, tongue, periorbital region, and extremities. Involvement of the upper airway constitutes a life-threatening emergency that demands immediate recognition and intervention.

In Australia, angioedema accounts for an estimated 1 in 500 emergency department (ED) presentations annually, with hospital admission rates for angioedema rising by approximately 2–3 % per year over the past decade. The increasing prevalence is attributed in part to widespread ACE-inhibitor prescribing — ACE inhibitors are among the most commonly dispensed medications on the Pharmaceutical Benefits Scheme (PBS), and ACE-inhibitor angioedema now represents 20–40 % of all angioedema ED presentations nationally.

Hereditary angioedema (HAE) is rare, with an estimated prevalence of 1 in 50,000 Australians; however, significant diagnostic delay (averaging 8–10 years from first symptom to diagnosis) suggests under-recognition. The Australian HAE patient registry data indicate that patients experience a mean of 4–6 attacks per year before commencing prophylaxis, with laryngeal involvement reported in up to 50 % of patients over their lifetime.

This guideline covers the classification, pathophysiology, diagnosis, and emergency management of angioedema in the Australian clinical context, with attention to PBS-listed therapies, state-based hospital protocols, and equity considerations for underserved populations.

Types of Angioedema

Accurate classification is essential because histamine-mediated and bradykinin-mediated angioedema require fundamentally different treatments. The major types encountered in Australian practice are summarised below.

Type	Mechanism	Common Triggers / Associations	Responds to Adrenaline / Antihistamines?
Allergic (histamine-mediated)	IgE-mediated mast-cell degranulation → histamine release	Foods (peanut, shellfish, egg), NSAIDs, latex, insect stings, antibiotics (penicillin)	Yes — first-line
Hereditary angioedema (HAE) Type I	Quantitative C1-inhibitor deficiency → unregulated kallikrein → excess bradykinin	Trauma, stress, dental procedures, OCP/oestrogens; often spontaneous	No
HAE Type II	Dysfunctional C1-inhibitor (normal or elevated levels, reduced function)	Same as Type I	No
HAE Type III (normal C1-INH)	Often factor-XII gain-of-function mutation; oestrogen-sensitive	Oestrogen-containing contraceptives, pregnancy	No
ACE-inhibitor angioedema	Bradykinin accumulation due to reduced degradation (ACE = kininase II)	Enalapril, ramipril, perindopril — may occur months–years after initiation	No
Acquired C1-inhibitor deficiency	Autoantibody consumption of C1-INH; associated with lymphoproliferative disorders	B-cell lymphoma, monoclonal gammopathy	No
Idiopathic	Unknown; may be histamine-mediated or bradykinin-mediated	Diagnosis of exclusion	Variable

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Critical distinction: Giving adrenaline, antihistamines, and corticosteroids to a patient with bradykinin-mediated angioedema (HAE or ACE-inhibitor) is ineffective and may delay appropriate therapy. Always consider bradykinin aetiology — especially if the tongue is involved without urticaria, or there is a family history or ACE-inhibitor use.

Pathophysiology

Histamine-Mediated (Allergic) Pathway

Allergen cross-links surface-bound IgE on mast cells and basophils, triggering degranulation and release of histamine, tryptase, prostaglandins, and leukotrienes. Histamine acts on H₁-receptors on vascular endothelial cells, causing endothelial cell contraction, intercellular gap formation, and plasma extravasation into the deep dermis and submucosa. The result is non-pitting oedema that is typically pruritic, often accompanied by urticaria, and resolves within 24–72 hours.

Bradykinin-Mediated Pathway

Bradykinin is a potent vasoactive nonapeptide generated by the action of kallikrein on high-molecular-weight kininogen (HMWK). C1-inhibitor (C1-INH) is the primary regulatory serine protease inhibitor (serpin) of this pathway — it inhibits activated factor XII (Hageman factor), plasma kallikrein, and C1s/C1r in the classical complement pathway.

In HAE Type I (~85 % of cases), reduced synthesis of C1-INH protein leads to uninhibited kallikrein activity and excess bradykinin production. In Type II (~15 %), C1-INH protein levels are normal or elevated but the molecule is dysfunctional. In both types, C4 is chronically low because of unregulated classical-pathway consumption.

ACE-inhibitor angioedema occurs because angiotensin-converting enzyme (ACE) is identical to kininase II — the primary enzyme responsible for bradykinin degradation. Inhibition of ACE raises local bradykinin concentrations, predisposing to angioedema. Individual susceptibility likely depends on polymorphisms in aminopeptidase P and neprilysin (alternative bradykinin-degradation pathways).

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Bradykinin acts on endothelial B₂-receptors (constitutive; blocked by icatibant) and B₁-receptors (inducible; upregulated by inflammation). Current targeted therapies exploit these receptors or replace deficient C1-INH.

Clinical Features & Diagnosis

Clinical Presentation

Angioedema presents with recurrent episodes of localised, non-pitting oedema affecting one or more of the following sites:

Face: Lips, periorbital region, cheeks — the most common site overall
Upper airway: Tongue, uvula, soft palate, larynx — potentially fatal; 25–50 % of HAE patients experience at least one laryngeal attack
Extremities: Hands, feet — can be debilitating and interfere with daily function
Gastrointestinal tract: Colicky abdominal pain, nausea, vomiting, diarrhoea — due to bowel-wall oedema; may mimic an acute abdomen
Urogenital: Genital swelling (more common in HAE)

Differentiating Histamine-Mediated from Bradykinin-Mediated Angioedema

Feature	Histamine-Mediated	Bradykinin-Mediated (HAE / ACE-I)
Urticaria	Usually present (≥ 90 %)	Absent
Pruritus	Prominent	Usually absent; may have tingling / tightness
Prodrome	None or sudden onset	Tingling, erythema marginatum (serpiginous, non-pruritic rash) in ~40 % of HAE
Onset to peak	Minutes to 1–2 hours	Gradual over 12–36 hours; untreated lasts 2–5 days
Response to adrenaline	Rapid improvement	Poor or absent
Family history	Atopy	Autosomal dominant (50 %); 25 % are de-novo mutations
Medications	NSAIDs, antibiotics	ACE inhibitors, oestrogens

Diagnostic Approach

The diagnostic algorithm depends on clinical context:

1

Clinical Assessment

History of urticaria, medications (ACE inhibitors, OCP), family history, recurrence pattern, age of first episode. Document all medications including over-the-counter and herbal products.

2

First-Line Blood Tests

Serum C4 level — universally low in HAE Types I and II (even between attacks). If C4 is normal, bradykinin-mediated HAE is effectively excluded. If C4 is low, proceed to Step 3.

3

C1-Inhibitor Assays

C1-INH antigenic level (quantitative) and C1-INH functional assay. Type I: low level + low function. Type II: normal/high level + low function. Both assays should be performed simultaneously. Available at major Australian reference laboratories (Sullivan Nicolaides, Douglass Hanly Moir, Melbourne Pathology).

4

If C1-INH Normal — Consider

HAE Type III (normal C1-INH): genetic testing for F12 (factor XII) mutations, available through specialist referral (Clinical Immunology). Acquired C1-INH deficiency: C1q level (low in acquired, normal in hereditary).

Investigations with Australian Availability

Available Serum C4 MBS item 65070 · Turnaround: 1–3 days · Screening test for all suspected bradykinin angioedema

Available C1-INH quantitative level MBS item 65095 · Reference lab assay · Confirmatory for HAE Type I vs II

Available C1-INH functional assay Specialist pathology request · Essential alongside quantitative level

Specialist C1q level Differentiates acquired (low C1q) from hereditary (normal C1q) C1-INH deficiency

Specialist F12 gene mutation testing Referred to clinical genetics / immunology · For suspected HAE Type III

Available Serum tryptase Collect within 1–2 hours of symptom onset · Elevated in mast-cell-mediated reactions; normal in bradykinin-mediated

Emergency Management

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Airway first: Any signs of upper-airway compromise (stridor, hoarseness, dyspnoea, tongue or uvula swelling) require immediate senior anaesthetic and/or ENT review. Do not delay intubation — progressive oedema may make intubation impossible within minutes. Have a surgical airway kit (cricothyroidotomy) at the bedside.

Immediate Resuscitation (All Angioedema Types)

1

Airway Assessment

Assess for stridor, voice change, inability to swallow secretions, tongue protrusion. Continuous SpO₂ monitoring. Call for senior help early — do not wait for deterioration.

2

High-Flow Oxygen

15 L/min via non-rebreather mask. Aim SpO₂ ≥ 94 %.

3

IV Access & Monitoring

Two large-bore IV cannulae. Continuous cardiac monitoring, BP every 5 minutes. Prepare for potential intubation or surgical airway.

Histamine-Mediated (Allergic) Angioedema — Acute Treatment

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Adrenaline (Epinephrine)

EpiPen® / Anapen® · Sympathomimetic

Adult dose 0.3–0.5 mg IM into anterolateral thigh (1:1000 = 1 mg/mL). Repeat every 5–15 min PRN.

Paediatric dose 0.01 mg/kg IM (max 0.3 mg in children < 30 kg; 0.5 mg if ≥ 30 kg)

Route Intramuscular (IM)

PBS status ✔ PBS General Benefit

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Dexchlorpheniramine

Polaramine® · H₁-antihistamine

Adult dose 5 mg IV/IM slow injection, repeat 6-hourly

Paediatric dose 0.125 mg/kg IV/IM (max 5 mg) 6-hourly

PBS status ✔ PBS General Benefit

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Hydrocortisone

Solu-Cortef® · Corticosteroid

Adult dose 200 mg IV bolus

Paediatric dose 4 mg/kg IV (max 200 mg)

PBS status ✔ PBS General Benefit

Bradykinin-Mediated Angioedema (HAE) — Acute Treatment

Standard allergy therapies (adrenaline, antihistamines, corticosteroids) are not effective for bradykinin-mediated attacks. Targeted therapies are required and should be administered as early as possible.

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C1-Inhibitor Concentrate (Human Plasma-Derived)

Berinert® · 500 IU vial · Replacement therapy

Adult dose 20 IU/kg IV over 10 minutes; max 100 IU/kg/day

Paediatric dose 20 IU/kg IV (same as adult)

Route Intravenous (IV) — slow infusion

Onset Symptom improvement within 30–60 minutes

PBS status Authority Required — Specialist · Available via Special Access Scheme (SAS Category B) through hospital pharmacies

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Icatibant

Firazyr® · 30 mg/3 mL pre-filled syringe · Bradykinin B₂-receptor antagonist

Adult dose 30 mg SC into abdominal wall; may repeat every 6 hours (max 3 doses/24 h)

Paediatric dose Not established for < 18 years in Australia; specialist use only

Route Subcutaneous (SC) — self-administration training available

PBS status Authority Required — Specialist · SAS Category B

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Tranexamic Acid

Cyklokapron® · Antifibrinolytic

Adult dose 1 g IV over 10 minutes; may be repeated after 1 hour if no response

Paediatric dose 20 mg/kg IV (max 1 g)

Role Second-line for HAE if C1-INH concentrate or icatibant unavailable; also used for long-term prophylaxis (1 g PO TDS)

PBS status ✔ PBS General Benefit

ACE-Inhibitor Angioedema — Management

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Permanently discontinue the ACE inhibitor. Do not rechallenge. Document clearly in the medical record and Allergies/Adverse Drug Reactions as a life-threatening reaction. Inform the patient, GP, pharmacist, and all treating specialists. Consider alerting via My Health Record adverse-reaction listing.

If the attack is bradykinin-mediated and targeted HAE therapies are available, consider icatibant or C1-INH concentrate under specialist guidance. Evidence is emerging but not yet definitive. Icatibant has shown benefit in small RCTs for ACE-inhibitor angioedema.

For ACE-inhibitor angioedema with airway compromise that is not responding to standard measures, discuss with the on-call immunologist or contact the Australian HAE Helpline (through HAE Australasia) for advice on emergency access to C1-INH concentrate.

Observation & Disposition

Mild

Isolated Facial / Extremity Swelling

No airway involvement, no dysphagia, no respiratory distress, responds to initial therapy within 2 hours.

Setting: ED observation 4–6 hours post-treatment; discharge with action plan, oral antihistamine, GP follow-up in 48 hours

Moderate

Tongue / Soft Palate Swelling Without Stridor

Mild dysphagia, globus sensation, visible uvula or tongue oedema but no airway compromise. Slow progression or incomplete response to initial therapy.

Setting: Hospital admission; continuous monitoring; ENT / anaesthetic review; repeat targeted therapy if bradykinin-mediated; observe minimum 24 hours

Severe

Airway Compromise / Laryngeal Angioedema

Stridor, severe dyspnoia, inability to handle secretions, rapidly progressive swelling, hoarseness / aphonia.

Setting: ICU / HDU; immediate senior anaesthetic involvement; prepare for intubation or surgical airway; IV adrenaline infusion if allergic; C1-INH or icatibant if HAE

Long-Term Prophylaxis for HAE

Long-term prophylaxis (LTP) is indicated for patients with ≥ 1 attack per month, significant disease burden, laryngeal attack history, or limited access to on-demand therapy. Options available in Australia:

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Danazol

Danocrine® · Attenuated androgen

Adult dose 200 mg PO daily; titrate to lowest effective dose (may reduce to 100 mg on alternate days)

Monitoring LFTs every 6 months; lipid profile; CBC; liver ultrasound annually

PBS status PBS Restricted Benefit

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Tranexamic Acid

Cyklokapron® · Antifibrinolytic — prophylactic dosing

Adult dose 1 g PO TDS (3 g/day total)

Paediatric dose 25 mg/kg PO TDS (max 1 g TDS)

Renal adjustment Reduce dose if eGFR < 30 mL/min

PBS status ✔ PBS General Benefit

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Subcutaneous C1-Inhibitor (Concentrated)

Haegarda® · Plasma-derived · SC prophylaxis

Adult dose 60 IU/kg SC twice weekly

Advantage Self-administered at home; steadier C1-INH levels than IV dosing

PBS status Authority Required — Specialist · SAS / compassionate access

Special Populations

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Pregnancy & Breastfeeding

HAE in pregnancy: Attack frequency may increase in the second and third trimesters. C1-INH concentrate is the preferred on-demand therapy (Category B2). Tranexamic acid may be continued but assess risk–benefit. Danazol is contraindicated (teratogenic — virilisation of female foetus).

Allergic angioedema: Adrenaline remains first-line in pregnancy — risk of untreated anaphylaxis outweighs theoretical fetal risk. Use lowest effective dose.

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Paediatric Considerations

HAE onset: Mean age of first attack is 8–12 years but may present as early as age 2. Recurrent abdominal pain in a child with family history of HAE warrants C4 screening.

Adrenaline autoinjectors: EpiPen® Jr (0.15 mg) for 15–30 kg; EpiPen® (0.3 mg) for > 30 kg. Train families in use.

Weight-based dosing for all emergency medications is critical — refer to APLS or local paediatric guidelines.

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Elderly Patients

Higher prevalence of ACE-inhibitor use — maintain a high index of suspicion for drug-induced angioedema, even if the medication has been taken for years without issue.

Corticosteroid side-effects (hyperglycaemia, delirium) require monitoring during prolonged treatment courses.

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Renal Impairment

Tranexamic acid: Dose reduction required if eGFR < 30 mL/min — risk of accumulation and seizures.

C1-INH concentrate: No renal adjustment required; safe in dialysis patients.

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Hepatic Impairment

Danazol: Contraindicated in significant hepatic disease; monitor LFTs closely in all patients.

C1-INH concentrate is safe — no hepatic dose adjustment.

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Immunocompromised Patients

Acquired C1-INH deficiency should be considered in patients with lymphoproliferative disorders presenting with new-onset angioedema.

Exclude infection-related triggers (e.g., hepatitis B/C associated cryoglobulinaemia).

Aboriginal and Torres Strait Islander Health Considerations

Aboriginal and Torres Strait Islander Health

Epidemiology & burden

Australian Institute of Health and Welfare (AIHW) data indicate that Aboriginal and Torres Strait Islander peoples experience higher rates of allergic disease and hospitalisation for anaphylaxis/angioedema compared with non-Indigenous Australians, though specific angioedema data remain limited. Medication-related angioedema is particularly relevant given high rates of cardiovascular disease and ACE-inhibitor prescribing in Indigenous health services.

Remote & rural access

Many communities are hours from the nearest hospital with anaesthetic or ENT capability. Laryngeal angioedema in a remote clinic setting is a critical emergency — the Royal Flying Doctor Service (RFDS) must be contacted immediately. Ensure community health centres stock adrenaline ampoules and are trained in IM injection technique. Telehealth consultation with a clinical immunologist (via the Australian Telehealth Network) can facilitate acute decision-making.

Medication access

Adrenaline autoinjectors (EpiPen® / Anapen®) are available under PBS for patients with a history of anaphylaxis, but cost and remoteness remain barriers. Advocate for patients to receive autoinjectors through Closing the Gap PBS co-payment provisions (no patient co-payment for eligible Indigenous patients). C1-INH concentrate access requires metropolitan hospital pharmacy — arrange RFDS transfer protocols for confirmed HAE patients in remote areas.

Diagnostic delay

HAE may be underdiagnosed in Indigenous Australians due to limited access to specialist immunology services and complement testing. Consider screening C4 level in any Indigenous patient with recurrent unexplained swelling, particularly with family history. Remote pathology services can perform C4 testing — arrange through local Aboriginal Health Worker or Remote Area Nurse.

Cultural safety

Engage Aboriginal Health Workers (AHWs) and Aboriginal Liaison Officers in patient education and care planning. Provide culturally appropriate written materials in plain English and, where possible, in relevant First Nations languages. Use the National Aboriginal Community Controlled Health Organisation (NACCHO) frameworks for chronic disease management. Respect kinship structures in family education about hereditary conditions — consider involving Elders where appropriate and with patient consent.

Action plans

Ensure all patients receive a written angioedema/anaphylaxis action plan adapted for the remote setting. Include clear instructions for community health workers on when to call RFDS. Register confirmed HAE patients with HAE Australasia for ongoing support and access to emerging therapies.

📚 References

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