Hereditary Angioedema (HAE) is a rare genetic disorder most often caused by a lack of a functional or sufficient amount of a protein called C1 esterase inhibitor (C1-INH). This protein is needed to help regulate several complex processes involved in immune system function, blood clotting, and bleeding. Without the correct level of C1-INH, a peptide called bradykinin is increased which may cause fluids to build up in body tissues (edema).
It is estimated that hereditary angioedema occurs in 1 in 10,000 to 1 in 50,000 people. Because it presents similarly to common illnesses, it can be difficult to diagnose.
Symptoms of hereditary angoedema include sudden recurrent attacks of swelling commonly affecting the hands, feet, arms, legs, face, abdomen, tongue and larynx (throat). Attacks involving the abdomen are often associated with severe pain, nausea and vomiting. Attacks of the larynx can lead to airway obstruction and can be life threatening. During an attack, swelling might occur in only one or multiple locations. The frequency, severity and location of attacks are often quite variable, even in the same patient.