,3,7 HAE includes HAE with C1–INH deficiency with low antigenic and functional C1–INH levels (type 1 HAE, HAE-1, 85% of cases), HAE due to C1–INH dysfunction (Type 2 HAE, HAE-2, 10% of cases), characterized by normal (or elevated) antigenic but low functional C1–INH levels, and HAE with normal C1–INH (about 5% of cases). Here, SERPING1 is linked to hereditary angioedema.