Strikingly, mutant FXII (Thr309Lys) from patients with hereditary angioedema type III (HAEIII), where O-linked glycosylation at position 309 is lost and inactivation by C1 esterase inhibitor during activation by plasmin is reduced (33, 34), is protected from CpaA inactivation (32). Here, PLG is linked to hereditary angioedema type 3.