Hereditary angioedema due to C1-inhibitor deficiency (C1-INH-HAE), an autosomal dominant disorder with recurrent attacks of edema spontaneously developing in any body location, is characterized by a large heterogeneity in its clinical expression, including the age at disease onset, the number and triggers of attacks, the severity and localization of edema, and prodromal signs and symptoms (1, 2). Here, SERPING1 is linked to C1 inhibitor deficiency.