Hereditary angioedema (HAE) is an autosomal dominant disorder (mostly hereditary, although 25% of cases are sporadic), which is caused by the deficiency or dysfunction of the serpin C1 esterase inhibitor (C1-INH, gene SERPING1)—known as Type 1 HAE (~85% of cases) and Type 2 HAE, respectively. Here, SERPING1 is linked to hereditary angioedema.