Hereditary angioedema (HAE) is a disabling and potentially life-threatening disorder characterized by recurrent attacks of swelling. It is often linked to a deficiency or lack of functionality of the C1 esterase inhibitor (C1-INH), which leads to elevated levels of bradykinin. However, HAE can also occur in the presence of normal levels and activity of C1-INH, which is known as nC1-INH-HAE. Up to 25% of nC1-INH-HAE cases exhibit mutations in the factor XII (FXII) gene that cause an increase in levels of activated FXII, which is involved in the production of bradykinin.