Beyond the known pathogenic mutations in F12 gene that are described as causative for HAE (c.983C>A, c.983C>G, c.971_10182 + 4del, c.892_909dup), a common polymorphism, c.-4T>C (F12-46C/T) is demonstrated to influence the severity of disease in patients with C1-INH-HAE (50). Here, SERPING1 is linked to hereditary angioedema.