,25 Both antigenic C1INH level and C1INH function are decreased in patients with HAE-C1INH-Type1, whereas patients with HAE-C1INH-Type2 have normal or elevated antigenic C1INH level but reduced C1INH function;1 therefore, fC1INH is essential for the diagnosis of HAE-C1INH-Type1 and HAE-C1INH-Type2.1 Here, SERPING1 is linked to hereditary angioedema.