Angioedema is the formal medical term for swelling under the skin. There are several types of angioedema, each with its own underlying cause or causes, but the end result — swelling — is the same.
Types of angioedema
Acute allergic angioedema occurs as part of an allergic reaction to various allergens or triggers. These can include certain foods, insect bites or stings, medications, and natural rubber products like latex.
Some medications, typically angiotensin-converting enzyme (ACE) inhibitors, can cause angioedema without triggering an allergic reaction. This is called non-allergic angioedema or drug-induced angioedema.
Hereditary angioedema, or HAE, is a rare form of angioedema caused by genetic mutations that a person inherits from a biological parent. HAE-causing mutations affect the production and/or function of one of two blood proteins: C1 inhibitor or coagulation factor 12. This disease is inherited in an autosomal dominant pattern, meaning that one copy of the mutated gene (inherited from either biological parent) is sufficient for a person to develop the condition.
In some cases, a person can develop abnormally low levels of the C1 inhibitor protein for reasons other than genetic mutations. For example, the immune system may erroneously attack this protein in certain circumstances. Such cases are called acquired angioedema.
Idiopathic angioedema refers to a particular type of angioedema that has no clear cause.
Causes of angioedema
Angioedema can be triggered by several factors, including allergic reactions, exposure to certain medications, inherited genetic mutations, be associated with other illnesses (e.g., infection or cancer), or be the result of an abnormal immune response. In some cases, particular causes are unknown.
Symptoms of angioedema
The hallmark symptom of angioedema is swelling in the skin and/or mucus membranes. This swelling occurs most commonly in the lips, face, tongue, neck, or genitals. In more severe instances, swelling can occur in the throat or intestines.
Angioedema also may occur alongside hives (urticaria), a condition that causes swelling in the upper layer of the skin, or alone. When triggered by an allergic reaction, angioedema often is accompanied by hives. While angioedema causes large, thick welts, which may not be itchy, to appear in the skin, hives normally result in the appearance of smaller bumps that usually are itchy.
Diagnosis of angioedema
Angioedema is diagnosed following examination of the affected area(s) and patients’ medical and family history.
Allergy tests, such as the skin prick test, may be performed when the condition is thought to be associated with an allergic reaction. If HAE is suspected, a blood test may be performed to check the levels of C1 inhibitor protein. In these cases, genetic testing also may be performed to search for potential disease-causing mutations.
Treatment depends on the severity and cause of the condition. Many cases of angioedema are short-lived and will clear up on their own without medication.
Angioedema due to an allergic reaction can be prevented by avoiding exposure to specific triggers, like certain types of food. Cases where the condition is associated with a non-allergic therapy reaction can be resolved by having patients switch to a medication that does not trigger angioedema.
Angioedema related to an allergy typically will be treated with antihistamine medications that dampen the allergic response. More severe cases may require treatment with anti-inflammatory drugs, such as oral corticosteroids.
Patients with a history of severe angioedema in the throat or tongue, or with a particularly serious allergic reaction, may be prescribed an EpiPen (epinephrine injection) to be used in case of emergency.
HAE typically does not respond to antihistamines or corticosteroids, and usually is treated with medications designed to regulate blood proteins. Acute HAE attacks are typically treated with intravenous C1 inhibitor concentrates, like Berinert and Cinryze. When these treatments are unavailable, fresh frozen plasma may be used.
Acquired angioedema is treated in a similar manner to HAE.
Last updated: July 6, 2021
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