Acquired angioedema (AAE) is divided into four groups: (1) AAE-I, resulting from paraneoplastic syndrome or development of autoantibodies which enhances cleavage of C1-INH, leading to C1-INH dysfunction; (2) AAE-II, resulting from autoimmune disease; (3) AAE associated with sex hormones, especially in pregnancy; and (4) drug-induced AAE, particular associated with ACE inhibitors or angiotensin receptor blockers. Here, SERPING1 is linked to acquired angioedema.