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 autoimmune 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 autoimmune 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.