Hereditary Angioedema (HAE) is a rare, chronic, potentially life-threatening genetic condition resulting from a deficiency in C1 Inhibitor protein. Estimates of the occurrence of HAE range from 1 in 50,000 to 1 in 150,000 people with roughly the same frequency in men and women. Most patients experience their first attack during childhood or adolescence. HAE symptoms include episodes of oedema (swelling) in various body parts including the hands, feet, face, genitalia, abdomen and airway. Patients often have bouts of severe abdominal pain, nausea and vomiting that is caused by swelling in the intestinal wall. Airway swelling is particularly dangerous and can lead to death by asphyxiation. Medical help should always be sought immediately in the event of any airway swelling.