Most cases of HAE are caused by mutations in the <i>SERPING1</i> gene encoding C1-inhibitor (C1-INH-HAE); however, mutation analysis identified seven further types of HAE: HAE with Factor XII mutation (FXII-HAE), with plasminogen gene mutation (PLG-HAE), with angiopoietin-1 gene mutation (ANGPT1-HAE), with kininogen-1 gene mutation (KNG1-HAE), with a myoferlin gene mutation (MYOF-HAE), with a heparan sulfate-glucosamine 3-sulfotransferase 6 (<i>HS3ST6</i>) mutation, and hereditary angioedema of unknown origin (U-HAE). Here, KNG1 is linked to hereditary angioedema.