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Angioedema is rapid swelling (edema) of the dermis (deep skin), subcutaneous tissue (fat), mucosa and submucosal tissues (gastrointestinal or other hollow organ lining) that was first described in 1882. It is characterized by repetitive episodes of asymmetric swelling, frequently of the face, lips, tongue, limbs/hands or feet, and genitals that lasts 24 to 60 hours without itching or hives. In the gastrointestinal lining it can cause severe pain and increased girth with or without diarrhea or vomiting leading to unnecessary abdominal or gynecologic surgery. In the respiratory tract including the mouth and throat it can interfere with speech or swallowing and cause life threatening asphyxiation. In the urinary tract it can prevent urination. In the hands or feet it can preclude the use of the hands or ability to walk. In the face the eyes can be swollen shut.
Its prevalence is 1 in 10,000 to 1 in 50,000 individuals. It is classified as:
| Acquired (swelling occurs over a few minutes) | Hereditary(HAE)-genetic mutation and usually manifests in the second decade of life (swelling occurs over 2 to 8 hours) |
|---|---|
| immunologic-IgE antibody mediated allergies to foods, drugs or particles in the air like pollen, autoimmune and caused by the body's release of histamine or antibodies against the C1-esterase inhibitor protein | type I-decreased levels of C1-esterase inhibitor protein in the blood, 85% of hereditary type |
| nonimmunologic- side effect to certain medications, particularly Angiotensin Converting Enzyme inhibitors, NSAIDs like motrin, advil or aspirin, birth control pills containing estrogen, food additives that cause increased bradykinin levels | type II-dysfunctional C1-esterase inhibitor protein in the blood, 15% of hereditary type |
| idiopathic-unknown cause | type III-abnormal factor XII in blood clotting cascade so it is more active |
| cancer such as carcinoid or blood cancers |
HAE attacks are caused by the production of large amounts of bradykinin, that is normally broken down by C1-esterase inhibitor protein, in the bloodstream.
In the absence of C1-esterase inhibitor protein activity (the yellow dots) bradykinin production continues uncontrolled. These patients are deficient in C1-esterase inhibitor protein so the metabolic pathway depicted in the above diagram goes into overdrive. FXII is factor XII a component of the blood clotting cascade. Bradykinin increases blood vessel diameter and pore size with leaking resulting in swelling of the tissue through which the blood vessels travel. It is so powerful that 1 microgram injected into the brachial artery increases arm blood flow 6 fold. Dental treatment, particularly tooth extraction, is a recognized trigger of HAE though symptoms may not manifest for many hours or even days after the procedure. A typical course resolves in 5 to 7 days, but in some patients, the clinical manifestations exist up to 6 weeks. Other known triggers are physical/psychological stress, fatigue, menstrual periods, pregnancy, trauma and having a breathing tube placed for anesthesia. 75% of patients with HAE have a relative who suffers from repetitive bouts of swelling. The remaining 25% are spontaneous without an affected relative. The diagnosis can be made by blood tests measuring the blood complement cascade proteins C1 and C4. Unlike allergic edema, HAE attacks do not respond to antihistamines, steroids or adrenaline including Epipens. The attacks vary in frequency, type and severity which contributes to delays in seeking treatment. 50% of HAE patients will have a laryngeal (voice box) attack within their lifetime, 40% of which are fatal if not treated emergently.
