Hereditary angioedema is a genetic disorder that results in repeated episodes of swelling under the skin.

Hereditary angioedema resembles angioedema caused by an allergic reaction. However, hives do not develop and the cause is different. Hereditary angioedema is a genetic disorder due to a deficiency or malfunction of C1 inhibitor. C1 inhibitor is part of the complement system, which is part of the immune system (see Biology of the Immune System: Complement System).

In acquired angioedema, another disorder including certain cancers (such as lymphoma) or autoimmune disorders (such as systemic lupus erythematosus [lupus] or dermatomyositis) cause a deficiency of C1 inhibitor.

In hereditary and acquired angioedema, swelling (angioedema) may be triggered by

• An injury
• A viral infection
• Certain foods
• Pregnancy
• Exposure to cold
• Stress, such as that due to anticipating or having a dental or surgical procedure

Symptoms and Diagnosis

Areas of the skin and tissue under the skin may swell, as may the membranes lining the mouth, throat, airways, and digestive tract. Typically, the swollen areas are slightly painful, not itchy. Hives do not appear. Nausea, vomiting, and cramps are common. Swelling in the windpipe can interfere with breathing.

Doctors diagnose the disorder by measuring C1 inhibitor levels or activity in a sample of blood.

Angioedema

Treatment

Certain drugs, such as ecallantide or purified C1 inhibitor (derived from human blood), can sometimes relieve the swelling. However, these drugs are not always available. Antihistamines and corticosteroids are not effective.

If the airway suddenly swells and people have difficulty breathing, the airway must be opened—for example, by inserting a breathing tube in the windpipe through the person's mouth or nose (intubation) or through a small incision in the skin over the trachea.

Stanozolol and danazol (which are synthetic male hormones) may help prevent subsequent attacks. These drugs may be given for a few days before and after a dental or surgical procedure, which may trigger an attack. Or they may be given to prevent attacks over the long term. These drugs, taken by mouth, can stimulate the body to produce more C1 inhibitor. Because these drugs can have masculinizing side effects, the dose is reduced as soon and as much as possible when these drugs are given to women for a long time.

Last full review/revision August 2012 by Peter J. Delves, PhD