COL18A1 and hereditary angioedema: Years later, a novel variant affecting function was described in exon 9 of the F12 gene, encoding the coagulation factor FXII, in some families affected by Bk-AE but without a C1-INH deficiency (HAE-nC1-INH; also known as HAE type III in the past) (Dewald and Bork, 2006).