Angioedema: causes, symptoms, diagnosis and treatment

Causes and types

Mechanisms include increased vascular permeability mediated by histamine, bradykinin, or incompletely understood pathways. Major categories are:

• Histamine‑mediated (allergic): often rapid after exposure to foods, insect stings, drugs or contact allergens; commonly occurs with urticaria and responds to antihistamines and corticosteroids.
• Bradykinin‑mediated: includes hereditary angioedema (HAE) due to C1‑inhibitor deficiency or dysfunction, angioedema caused by ACE inhibitors, and acquired C1‑inhibitor deficiency. These attacks tend not to itch and do not respond to antihistamines or steroids.
• Idiopathic and other: recurrent angioedema without an identified trigger after evaluation; can be chronic and requires specialist assessment.

Typical symptoms and examination

Common sites are the face (lips, eyelids), oral cavity, tongue, larynx, extremities and genitalia. Swelling is often nonpitting, may be painful or tense, and can be accompanied by abdominal pain or vomiting when the bowel wall is involved, particularly in HAE. Airway symptoms include throat tightness, hoarseness, change in voice, stridor or progressive breathlessness.

Diagnosis and investigations

Diagnosis is primarily clinical. Important clues include timing after exposures, presence or absence of urticaria, family history, and medication history (notably ACE inhibitors). When HAE is suspected, complement testing (C4 and C1‑inhibitor level and function) is informative. Further allergy testing or specialist referral is appropriate for recurrent or unexplained cases, and evaluation for possible underlying disorders is needed in acquired forms.

Treatment and emergency care

Immediate priorities are protecting the airway and treating life‑threatening reactions. For suspected anaphylaxis or airway compromise, intramuscular epinephrine, oxygen, and advanced airway management are central. Other treatments depend on mechanism:

• Histamine‑mediated: antihistamines, systemic corticosteroids and epinephrine for severe reactions.
• Bradykinin‑mediated: do not respond to antihistamines or steroids; episode‑specific therapies used in specialist settings include C1‑inhibitor replacement, kallikrein inhibitors or bradykinin B2‑receptor antagonists, and stopping offending drugs (for example ACE inhibitors).

Prevention, follow up and prognosis

Avoiding known triggers and maintaining an emergency action plan are important. People with recurrent or severe angioedema should have specialist follow‑up, an individualized management plan and, if indicated, access to on‑demand and prophylactic therapies. Most isolated episodes resolve over hours to days, but airway involvement can be fatal without prompt treatment.