Genetic Disease

What is Hereditary Angioedema?

Hereditary angioedema (HAE) is a poorly known inherited disorder that can cause significant swelling in different parts of the body, such as the abdomen and face. Depending on the severity of the disease, some individuals will experience multiple crisis, while others will see months or even years pass without experiencing swelling attacks.

Doctors refer to this type of swelling as edema. In HAE, this edema is caused by a malfunction or an insufficient amount of a protein called C1-esterase inhibitor (C1-INH). C1-INH is part of the body’s immune system, which recognizes and attacks foreign invaders, such as viruses or bacterias.

C1-INH is involved in several different reactions of the immune system. Without an adequate amount of C1-INH, blood vessels may become less permeable and leaks may occur, allowing fluid to build up in the tissues, resulting in swelling. In HAE, this swelling can occur almost anywhere in the body, but is most often seen in one of the following areas:


  • Extremities (hands, feet, arms, legs)
  • Intestines (abdomen)
  • Face;
  • Larynx (throat);
  • Genitals


Unlike allergic reactions, which affect both sides of the body, HAE attacks can occur only on one side of the body. Example, only the right hand becomes swollen, not the left, or vice versa. Moreover, those crises can be debilitating. For example, swelling affecting the intestines can cause severe abdominal pain, even more painful than childbirth.

However, the most serious attacks are those that affect the throat or larynx. These laryngeal crisis can be life-threatening as they can prevent air supply to the lungs, cause a respiratory arrest, even cause death.