Factor V mutation illuminates the dominant anticoagulant role and importance of an unidentified platelet modifier

Coagulation factor (F)V is a critical procoagulant protein, functioning as a cofactor in the prothrombinase complex. However, FV is also an anticoagulant protein, serving as a cofactor for activated protein C (APC) and for tissue factor pathway inhibitor (TFPI)α. Presently, the balance and relative importance of these opposing functions of FV is not well understood. In this issue of J Thromb Haemost, Castoldi et al. investigated a patient who is...