SERPING1 and angioedema: Hereditary angioedema (HAE) is a rare genetic disorder caused by either a deficiency or dysfunction of the C1 esterase inhibitor (C1-INH) gene, which underlies both type I and type II HAE, as well as the existence of hereditary angioedema with normal C1-INH activity (type III HAE) [1,2,3,4,5].