SERPING1 and hereditary angioedema: Hence, the following types of HAE can be differentiated today: (a) hereditary angioedema due to a genetic C1-INH deficiency (HAE-C1-INH) including type I and type II; and (b) hereditary angioedema with normal C1-INH (HAE type III) including hereditary angioedema due to the two known mutations in the coagulation factor XII gene (HAE-FXII) and hereditary angioedema with an unknown genetic cause (normal C1-INH activity in plasma, no causative mutation in the gene coding for C1-INH and none of the known FXII gene mutations Thr309Lys or Thr309Arg) (HAE-unknown).