SERPING1 and acquired angioedema: AAE-C1INH typically arises in persons older than 40 years and is thought to result either from increased clearance of C1-inhibitor (C1INH) by autoantibodies, which are identified in 47% to 67% of patients,2 or from increased consumption of C1INH leading to activation of the classical complement pathway by anti-idiotype antibodies.