Angioedema

Angioedema is non-pitting, non-dependent, transient swelling of the subcutaneous or submucosal tissues due to increased vascular permeability. The critical clinical distinction is between histamine-mediated and bradykinin-mediated forms, as treatment differs fundamentally. [1-2]

The following figure illustrates the pathophysiology of bradykinin-mediated angioedema and the targets for available therapies:

1. History

• Onset and tempo: Histaminergic angioedema develops rapidly (minutes); bradykinin-mediated angioedema evolves more slowly (hours) [4]
• Location of swelling: Face, lips, tongue, oropharynx, extremities, genitalia, abdomen
• Pruritus/urticaria: Presence strongly suggests histaminergic etiology; absence raises concern for bradykinin-mediated disease [2][5]
• Triggers: Allergen exposure (food, insect sting, drug), stress, trauma, dental procedures, estrogen-containing medications, menstruation (HAE)
• Medication history: ACE inhibitors (can occur at any time, even years after initiation), ARBs (less common), NSAIDs, aspirin [6-7]
• Prior episodes: Recurrence pattern, frequency, duration (HAE attacks typically last 2–5 days untreated)
• Abdominal symptoms: Crampy abdominal pain, nausea, vomiting, diarrhea — classic for HAE abdominal attacks, can mimic acute abdomen [4][7]
• Important negatives: No urticaria, no identifiable allergen, no response to antihistamines → think bradykinin-mediated [2]

2. Alarm Features

• Tongue swelling (especially anterior tongue), voice changes/hoarseness, stridor, drooling, dyspnea — all associated with need for intubation [8]
• Rapid symptom progression within 6 hours of onset — higher intubation risk in ACEi-angioedema [8]
• Floor of mouth or base of tongue involvement — high risk for airway compromise [2]
• Involvement of ≥3 head/neck sites (lips, anterior tongue, floor of mouth, soft palate, base of tongue, larynx) — increased risk of airway intervention [2]
• Laryngeal edema — the primary cause of death in HAE (estimated mortality up to 30% in undiagnosed patients) [6]
• Angioedema unresponsive to epinephrine, antihistamines, and steroids — suggests bradykinin-mediated etiology requiring targeted therapy [2][9]

3. Medications

Causative/Contributing Medications

• ACE inhibitors — most common drug-induced cause; incidence 0.1–0.7%; higher risk in African Americans and immunosuppressed patients [2][7]
• ARBs — less commonly associated; modest cross-reactivity risk [7]
• NSAIDs/Aspirin — can trigger histaminergic angioedema via mast cell degranulation [2]
• Estrogen-containing medications (OCPs, HRT) — can exacerbate HAE attacks [7]

Treatments — Histamine-Mediated

• Epinephrine 0.3–0.5 mg IM (weight-based: 150 µg if >10 kg, 300 µg if >30 kg) — first-line for anaphylaxis/severe allergic angioedema [9]
• H1 antihistamines (diphenhydramine 25–50 mg IV/IM, cetirizine)
• H2 antihistamines (famotidine 20 mg IV)
• Corticosteroids (methylprednisolone 125 mg IV or dexamethasone 10 mg IV)

Treatments — Bradykinin-Mediated (HAE)

• C1-INH concentrate (Berinert) — 20 U/kg IV [2]
• Icatibant (Firazyr) — 30 mg SC; may repeat q6h, max 3 doses/24h [2][10]
• Ecallantide (Kalbitor) — 30 mg SC (3 × 10 mg); must be given by healthcare professional due to ~3% anaphylaxis risk [2]
• Sebetralstat (Ekterly) — oral plasma kallikrein inhibitor, FDA-approved for acute HAE attacks in patients ≥12 years; first oral on-demand therapy [10]
• Fresh frozen plasma — if targeted therapies unavailable; carries risk of worsening symptoms in HAE [4][7]

Contraindicated in HAE

• Androgens are contraindicated in pregnancy [7]
• Standard angioedema treatments (epinephrine, antihistamines, steroids) are ineffective for bradykinin-mediated angioedema but are not contraindicated and should be given if etiology is uncertain [2]

4. Diet

• No specific dietary triggers for most angioedema subtypes
• Allergic angioedema: Identify and avoid food allergens (nuts, shellfish, eggs, etc.)
• HAE abdominal attacks: Aggressive IV hydration due to third-space fluid losses; NPO if acute abdomen is being ruled out [7]
• Long-term: Patients with histaminergic angioedema may benefit from low-histamine diets in select cases

5. Review of Systems

• Respiratory: Dyspnea, stridor, voice change, sensation of throat tightness or closure
• GI: Abdominal pain, nausea, vomiting, diarrhea (HAE abdominal attacks can mimic surgical abdomen) [4]
• Skin: Urticaria, pruritus (present → histaminergic; absent → bradykinin-mediated) [5]
• Cardiovascular: Hypotension, tachycardia (anaphylaxis)
• Genitourinary: Genital swelling (common in HAE)
• Constitutional: Prodromal symptoms — erythema marginatum (serpiginous, non-pruritic rash) can precede HAE attacks

6. Collateral History and Family History

• Family history of angioedema — HAE is autosomal dominant; ~75% have positive family history, but ~25% are de novo mutations [6][11]
• Family history of unexplained death (laryngeal edema), recurrent abdominal surgeries, or recurrent swelling episodes
• Age of onset: HAE typically presents before age 20; acquired C1-INH deficiency usually presents after age 40 [2]
• Known HAE patients may carry their own on-demand medications and can communicate their diagnosis [5]
• Social context: Occupation, ability to self-administer rescue medications, access to emergency care

7. Risk Factors

• ACEi-angioedema: African American race (4–5× higher risk), immunosuppressive therapy, history of seasonal allergies, female sex [2][7]
• HAE: Family history, SERPING1 gene mutation, female sex (estrogen-sensitive), trauma/dental procedures, emotional stress, infections [6]
• Acquired C1-INH deficiency: Underlying lymphoproliferative disorder, autoimmune disease, age >40 [6-7]
• Histaminergic: Atopy, known allergies, prior anaphylaxis, NSAID use

8. Differential Diagnosis

Cannot-Miss Diagnoses

• Anaphylaxis — urticaria + angioedema + hypotension/bronchospasm; requires immediate epinephrine
• Laryngeal/epiglottic pathology — epiglottitis, peritonsillar abscess, retropharyngeal abscess
• Superior vena cava syndrome — facial/neck swelling with venous distension

Key Differentials

• ACEi-induced angioedema vs. HAE vs. allergic angioedema — the critical ED distinction [2]
• Acquired C1-INH deficiency — mimics HAE but onset >40 years, associated with lymphoproliferative/autoimmune disease [6-7]
• Idiopathic angioedema — largest category; diagnosed by exclusion [6]

Mimics

• Anasarca (pitting, dependent, persistent) [2]
• Myxedema (hypothyroidism)
• Contact dermatitis/cellulitis — erythematous, warm, tender
• Cheilitis granulomatosa (Melkersson-Rosenthal syndrome) [12]
• Hypocomplementemic urticarial vasculitis [12]
• Gleich syndrome (episodic angioedema with eosinophilia)

9. Past Medical History

• Prior angioedema episodes — frequency, severity, sites, response to treatment
• Known HAE diagnosis — type, current prophylactic regimen, on-demand therapy available
• ACE inhibitor or ARB use (current or past)
• History of atopy, asthma, allergic rhinitis, food allergies
• Lymphoproliferative or autoimmune disorders (acquired C1-INH deficiency)
• Prior intubations or surgical airways for angioedema
• Prior unnecessary laparotomies (HAE abdominal attacks misdiagnosed as surgical abdomen)

10. Physical Exam

Vital Signs

• Tachycardia, hypotension → anaphylaxis
• Tachypnea, stridor, desaturation → impending airway compromise

Focused Exam

• Airway: Voice quality, ability to handle secretions, drooling, stridor, tongue protrusion, floor of mouth swelling
• Oropharynx: Uvular edema, soft palate swelling, base of tongue involvement
• Skin: Non-pitting, non-dependent swelling of lips, face, periorbital area, extremities, genitalia; presence or absence of urticaria/wheals [2]
• Abdomen: Tenderness, distension (HAE abdominal attacks) — may mimic peritonitis [4]
• Key distinction: Angioedema is non-pitting and non-dependent vs. edema which is pitting and dependent [2]

11. Lab Studies

No point-of-care labs provide immediate ED guidance, but the following should be drawn during an acute attack for outpatient follow-up: [2]

• C4 level — best screening test for C1-INH deficiency; low in virtually 100% of HAE type I/II during attacks (95% between attacks) [2][7]
• C1-INH antigenic level — low in type I HAE, normal/elevated in type II HAE [3]
• C1-INH functional level (chromogenic assay preferred) — low in both type I and type II HAE [3][7]
• C1q level — normal in HAE; low in acquired C1-INH deficiency (helps distinguish the two) [7]
• Serum tryptase — elevated in anaphylaxis/mast cell-mediated angioedema; normal in HAE [2]
• CBC, BMP — baseline; hemoconcentration may occur with significant third-spacing
• Do NOT screen with CH50 or C3 [2]

12. Imaging

• Radiographic airway assessment has limited utility in acute angioedema and may impose unnecessary risk from delays and reduced monitoring [2]
• Flexible fiberoptic nasopharyngoscopy — recommended for all patients with head/neck angioedema with lingual involvement or upper airway complaints to assess base of tongue and larynx [2]
• CT abdomen — may show bowel wall edema/ascites in HAE abdominal attacks; useful to rule out surgical pathology if diagnosis uncertain
• Lateral neck X-ray — generally not recommended; delays care

13. Special Tests

Diagnostic Scoring/Staging

• Ishoo Classification (stages I–IV) — risk stratification based on anatomic involvement; guides disposition, though not yet validated: [2]
  • Stage I: Facial/lip edema only
  • Stage II: Soft palate edema
  • Stage III: Lingual edema
  • Stage IV: Laryngeal edema

Point-of-Care

• Bedside flexible nasopharyngoscopy — most important ancillary test in the ED [2]
• No validated POC tests for angioedema subtype differentiation

Genetic Testing

• SERPING1 gene sequencing — for HAE confirmation, family screening, and HAE with normal C1-INH [6][13]
• Factor XII, plasminogen, angiopoietin-1, kininogen-1, myoferlin, or heparan sulfate gene mutations — for HAE with normal C1-INH [6]

14. ECG

• Indicated if anaphylaxis is suspected — monitor for arrhythmias, ischemia from epinephrine administration or hemodynamic compromise
• Epinephrine-related changes: Sinus tachycardia, ST changes, QTc prolongation
• Kounis syndrome: Allergic angina — ST elevation in the setting of anaphylaxis
• Routine ECG not required for isolated peripheral angioedema without hemodynamic compromise

15. Assessment

Classification Framework: [2][14]

• Histamine-mediated (most common ED presentation): Allergic, idiopathic, drug-induced (NSAIDs); typically with urticaria; responds to standard therapy
• Bradykinin-mediated (critical to recognize): HAE types I/II, HAE with normal C1-INH, acquired C1-INH deficiency, ACEi-induced; no urticaria; does NOT respond to antihistamines/steroids/epinephrine [2][9]

Severity Stratification

• Mild: Isolated lip/facial swelling, no airway involvement
• Moderate: Tongue swelling, soft palate involvement, mild voice change
• Severe: Laryngeal involvement, stridor, respiratory distress, hemodynamic instability

Complications

• Asphyxiation from laryngeal edema — leading cause of death in HAE [6]
• Unnecessary laparotomy from misdiagnosed abdominal HAE attacks
• Narcotic dependence from recurrent painful abdominal attacks [7]

16. Treatment Plan

Initial Stabilization (all types)

• ABCs — airway assessment is the immediate priority
• Continuous monitoring: SpO2, cardiac, clinical reassessment
• Supplemental O2, nasal trumpet, BVM as temporizing measures [2]

If etiology unknown — treat empirically

• Epinephrine 0.3–0.5 mg IM → H1 blocker (diphenhydramine 50 mg IV) + H2 blocker (famotidine 20 mg IV) → methylprednisolone 125 mg IV [2]
• If no response → suspect bradykinin-mediated etiology

Histamine-Mediated Angioedema

• Epinephrine IM (if severe/anaphylaxis)
• H1 + H2 antihistamines
• Corticosteroids
• IV fluids for anaphylaxis

Bradykinin-Mediated / HAE

• C1-INH concentrate (Berinert 20 U/kg IV) [2]
• Icatibant 30 mg SC (may repeat q6h, max 3 doses/24h) [2]
• Ecallantide 30 mg SC (healthcare professional only; observe 60 min for anaphylaxis) [2]
• Sebetralstat (oral, for patients ≥12 years) — first oral on-demand option [10]
• FFP 2 units if targeted therapies unavailable (risk of worsening) [4]
• Treat early — all attacks should be considered for treatment regardless of location or severity [15]

ACEi-Induced Angioedema

• Discontinue ACE inhibitor immediately [7]
• Supportive airway management
• Targeted HAE therapies (icatibant, C1-INH) have been used with variable results but are not formally recommended [4]
• Recurrence can occur weeks to months after ACEi discontinuation [6]

Airway Management

• Fiberoptic or video laryngoscopy preferred for intubation (distorted anatomy) [1]
• Have cricothyrotomy equipment at bedside [2]
• Awake intubation may be preferred; avoid paralytics if possible until airway is secured

17. Disposition

Admission Criteria (based on Ishoo staging): [2]

• ICU admission: Stages III–IV (lingual/laryngeal edema), respiratory distress, any patient requiring airway intervention
• Inpatient/observation: Stage II (soft palate edema), involvement of ≥3 head/neck sites, bradykinin-mediated angioedema with ongoing symptoms
• Extended ED observation: New-onset angioedema of uncertain etiology, ACEi-angioedema with tongue involvement

Discharge Criteria

• Stage I (face/lip only) with symptom resolution and no airway involvement [2]
• Known histaminergic angioedema with complete response to treatment
• Known HAE patient with mild attack responding to on-demand therapy

Specialist Consultation Triggers

• Suspected or confirmed HAE → Allergy/Immunology referral [5]
• Acquired C1-INH deficiency → Hematology/Oncology workup for lymphoproliferative disease [7]
• Airway compromise → Anesthesia, ENT, or surgical airway team
• Recurrent idiopathic angioedema unresponsive to antihistamines → Angioedema specialist [16]

18. Follow Up / Return Precautions

Discharge Instructions

• HAE patients: Ensure on-demand therapy is available for self-administration; provide refresher training [2]
• ACEi-angioedema: Discontinue ACE inhibitor permanently; arrange PCP follow-up for alternative antihypertensive (CCB or ARB generally safe, though modest recurrence risk exists with ARBs) [2]
• All patients: Discharge with epinephrine auto-injector if no targeted therapy available [2]

Return Precautions — Seek immediate care for

• Any throat tightness, voice change, difficulty swallowing or breathing
• Tongue swelling or sensation of tongue enlargement
• Worsening or recurrence of swelling despite treatment
• Abdominal pain with vomiting (HAE patients)

Follow-Up Timing

• Allergy/Immunology within 1–2 weeks for new-onset angioedema without clear etiology
• PCP within 48–72 hours for medication changes (ACEi discontinuation)
• HAE patients: Ensure connection with HAE specialist for long-term prophylaxis discussion

Expected Course

• Histaminergic angioedema typically resolves within 24–48 hours with treatment
• Bradykinin-mediated angioedema may last up to 5–7 days untreated; treated attacks resolve faster with early intervention [2][15]
• ACEi-angioedema may recur for weeks to months after drug discontinuation [6]

References

1. Evaluation and Management of Angioedema in the Emergency Department. — Long BJ, Koyfman A, Gottlieb M. The Western Journal of Emergency Medicine. 2019.

2. A Consensus Parameter for the Evaluation and Management of Angioedema in the Emergency Department. — Moellman JJ, Bernstein JA, Lindsell C, et al. Academic Emergency Medicine : Official Journal of the Society for Academic Emergency Medicine. 2014.

3. Hereditary Angioedema. — Busse PJ, Christiansen SC. The New England Journal of Medicine. 2020.

4. Angioedema and Emergency Medicine: From Pathophysiology to Diagnosis and Treatment. — Depetri F, Tedeschi A, Cugno M. European Journal of Internal Medicine. 2019.

5. Recognition and Differential Diagnosis of Hereditary Angioedema in the Emergency Department. — Pines JM, Poarch K, Hughes S. The Journal of Emergency Medicine. 2021.

6. Angioedema Without Urticaria: Diagnosis and Management. — Young MC, Banerji A. Allergy and Asthma Proceedings. 2025.

7. A Focused Parameter Update: Hereditary Angioedema, Acquired C1 Inhibitor Deficiency, and Angiotensin-Converting Enzyme Inhibitor-Associated Angioedema. — Zuraw BL, Bernstein JA, Lang DM, et al. The Journal of Allergy and Clinical Immunology. 2013.

8. Emergency Department Evaluation of Patients With Angiotensin Converting Enzyme Inhibitor Associated Angioedema. — Mudd PA, Hooker EA, Stolz U, et al. The American Journal of Emergency Medicine. 2020.

9. Angioedema. — Hahn J, Hoffmann TK, Bock B, et al. Deutsches Arzteblatt International. 2017.

10. FDA Orange Book. — FDA Orange Book. 2026.

11. Acute Upper Airway Obstruction. — Eskander A, de Almeida JR, Irish JC. The New England Journal of Medicine. 2019.

12. Unraveling Angioedema: Diagnostic Challenges and Emerging Therapies. — Johnson F, Hofauer B. Frontiers in Immunology. 2025.

13. Interventions for the Long-Term Prevention of Hereditary Angioedema Attacks. — Beard N, Frese M, Smertina E, et al. The Cochrane Database of Systematic Reviews. 2022.

14. Definition, Acronyms, Nomenclature, and Classification of Angioedema (DANCE): AAAAI, ACAAI, ACARE, and APAAACI DANCE Consensus. — Reshef A, Buttgereit T, Betschel SD, et al. The Journal of Allergy and Clinical Immunology. 2024.

15. Interplay Between on-Demand Treatment Trials for Hereditary Angioedema and Treatment Guidelines. — Cohn DM, Soteres DF, Craig TJ, et al. The Journal of Allergy and Clinical Immunology. 2025.

16. Isolated Angioedema: A Review of Classification and Update on Management. — Kesh S, Bernstein JA. Annals of Allergy, Asthma & Immunology : Official Publication of the American College of Allergy, Asthma, & Immunology. 2022.