Hereditary Angioedema, or HAE, is a very rare and potentially life-threatening genetic condition that involves recurrent attacks of severe swelling (angioedema) in various parts of the body, including the hands, feet, genitals, stomach, face and/or throat. Swelling in the airway can restrict breathing and be fatal. Episodes may be triggered by physical trauma or emotional stress, however, swelling often occurs without a known trigger.

Symptoms of HAE usually appear early in life, most often by age 13, and may increase in severity after puberty. Because HAE is so rare, it can take as long as a decade to obtain an accurate diagnosis after symptoms are first experienced.

When untreated, an HAE attack often lasts for three days, sometimes even longer, and many people with HAE experience three or more swelling attacks per month. The frequency and severity of attacks vary significantly among individuals, even among affected family members.

The vast majority of people with HAE have a genetic defect that causes a deficiency in the plasma protein called C1-Inhibitor. HAE is also seen in people who have normal levels of C1-Inhibitor, however, genetic defects in other genes cause their angioedema.