The Online Encyclopedia and Dictionary






Factor VIII

Factor VIII (FVIII) is an essential clotting factor. The lack of normal FVIII causes Hemophilia A, an inherited bleeding disorder.



The gene for Factor VIII is located on the X chromosome (Xq28).


FVIII is a glycoprotein synthesized and released into the bloodstream by the liver. In the circulating blood, it is mainly bound to von Willebrand factor (vWF, also known as Factor VIII-related antigen) to form a stable complex. Upon activation by thrombin, it dissociates from the complex to interact with other factors of the coagulation cascade. It is a cofactor to Factor IX in the activation of Factor X, which in turn activates more thrombin. Thrombin leads to fibrin formation and the development of a clot.

No longer protected by vWF, activated FVIII is proteolytically inactivated in the process (most prominently by activated Protein C) and quickly degraded.

Therapeutic use

FVIII harvested from donated blood or Recombinant FVIII can be given to hemophiliacs to restore hemostasis. Thus, FVIII is also known as Anti-Hemophilic Factor.

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Last updated: 10-29-2005 02:13:46