In case of C1‐INH‐AAE, the classical pathway of the complement system is activated and the C1‐INH consumption is increased, which can be attributed to lymphoproliferative, tumorous, autoimmune, or infectious diseases, but autoantibodies against C1‐INH may also lead to inadequate C1‐INH function.15 This evidence concerns the gene SERPING1 and infectious disease.