What Is Hereditary Angioedema?

Hereditary angioedema (HAE) is a rare inherited disease that causes considerable swelling in various body tissues, such as the abdomen or face. Depending on the severity of the disease, some people will have many attacks each month, while others will go months or even years without a swelling attack.

Doctors refer to this kind of swelling as edema (EH-deem-uh) . In HAE, this edema is caused by the poor functioning or lack of a protein called C1 esterase inhibitor (C1-INH). C1-INH is part of the immune system — the system of the body that recognizes and attacks foreign invaders, such as viruses or bacteria.

C1-INH is involved in many different reactions in the immune system. Without adequate amounts of C1-INH, blood vessels can become leaky, allowing fluid to build up in the tissue. In HAE, this swelling can occur almost anywhere but is often found in one of the following body parts:

  • Extremities (hands, feet, arms, legs)
  • Intestines (abdomen)
  • Face
  • Larynx, or voice box
  • Genitals

Unlike allergic reactions, in which both sides of the body are affected, HAE attacks may involve just one side of the body, for example, the right hand but not the left hand, or vice versa. In addition, these attacks can be disabling. For example, swelling of the intestines usually causes severe abdominal pain.

Most serious, however, are attacks of the voice box or larynx. These laryngeal attacks may be life-threatening because they can cut off the air supply to the lungs.

Identifying types of HAE

There are three main types of HAE:

  • Type I: Overall levels of C1-INH are low in type I HAE. About 85% of people with HAE have type I, making it the most common type. It occurs equally among men and women.
  • Type II: In type II HAE, the C1-INH levels are normal, but the existing C1-INH does not function properly. About 15% of people with HAE have type II, making it the second most common type of HAE. It occurs equally among men and women.
  • Type III: In type III HAE, C1-INH lab tests are normal, but the person has symptoms of HAE. This is an extremely rare type, and is not entirely understood. Type III HAE occurs most often in women.

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Checking your symptoms

The symptoms of HAE are similar to other medical conditions. But there are clues to help you identify this rare disease. Find out more about checking your symptoms.

Understanding HAE video

Hear what experts have discovered about hereditary angioedema, see why it is often misunderstood and misdiagnosed, and learn about new approaches to therapy. View the understanding HAE video.