Factor 5 Deficiency in Hemorrhagic Diathesis (Parahemophilia)

Normal plasma has been reported to contain a globulin which is a highly active accelerator of blood clotting. This factor acts by catalyzing the interaction of prothrombin, thromboplastin, and calcium in the formation of thrombin. In the absence of this factor blood clotting is delayed markedly. Owren1in 1944 discovered this new factor, which he called the fifth coagulation factor, or Factor 5. Fantl and Nance2and Ware, Guest, and Seegers3also demonstrated this new factor and its mechanism of action, calling it "accelerator globulin" or Ac-globulin. Quick's labile factor4may be very similar to or identical with Factor 5. In vivo deficiency of this factor was reported by Owren1as the mechanism of a hemorrhagic diathesis in a 29-year-old woman. This deficiency of Factor 5, considered to be congenital, characteristically was associated with a prolonged clotting time of venous blood and a prolonged one-stage