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.1

In HAE, these swelling episodes are referred to as angioedema, a rapidly progressing form of edema (EH-deem-uh) , which is an excess of watery fluid collecting in body tissue. People with HAE are missing or have low levels of a protein called C1 esterase inhibitor (C1-INH); in some cases, the C1-INH levels are sufficient but the protein does not function properly. C1-INH is part of the autoimmune system-the system of the body that recognizes and attacks foreign invaders, such as viruses or bacteria.2

C1-INH is involved in many different reactions in the autoimmune system. Without adequate amounts of C1-INH, functioning C1-INH activation of the complement system becomes uncontrolled, leading fluid to build up in body tissues, causing angioedema.2 HAE attacks can affect many parts of the body and can spread to multiple sites, though in many cases the attacks affect only one body part at a time. The following body parts are the most common sites of HAE attacks:3

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

HAE attacks generally self-resolve within 2 to 4 days and are sometimes very mild. However, patients who suffer gastrointestinal attacks of HAE can have abdominal pain, colic, nausea and vomiting; and misunderstanding of the cause has led to unneeded treatments and even surgeries. 1

Most serious, however, are attacks affecting the voice box or larynx. These laryngeal attacks may be life-threatening because they can cut off the air supply to the lungs.1

Identifying types of HAE

According to the US Hereditary Angioedema Association(HAEA), 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.1
  • 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.1
  • HAE with normal C1-INH, previously known as Type III: In extremely rare cases, C1-INH lab tests show normal levels but the person still has symptoms of HAE, a situation that as yet is not entirely understood. This type of HAE is more common in women.2

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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