Acquired angioedema with C1-inhibitor deficiency (AAE-C1-INH) is also characterized by decreased C1-INH and C4 levels, as well as by altered C1-INH function, but it is accompanied by decreased levels of C1q and, in a large percent of cases, the presence of anti-C1-INH antibodies. This evidence concerns the gene SERPING1 and acquired angioedema.