HAE can be caused by C1 inhibitor (C1-INH) deficiency (Type 1 HAE, HAE-1), C1-INH dysfunction (Type 2 HAE, HAE-2), or other mechanisms (HAE with normal C1-INH, HAE-nC1-INH). The gene discussed is SERPING1; the disease is hereditary angioedema with C1Inh deficiency.