Heavy chain of FXII: not an innocent bystander!

In this issue of null Blood , Ivanov et al 1 null have identified that the N-terminal noncatalytic heavy chain of factor XII (FXII) plays an important role in the regulation of activation of the contact pathway of coagulation by the reciprocal activation of FXII and prekallikrein (PK). This mechanism provides insights into the clinical manifestation of an edema outbreak in patients with a rare form of hereditary angioedema...