(Can also be known as Owren’s disease, labile factor deficiency, proaccelerin deficiency or parahemophilia. Not to be confused with Factor V Leiden, which is a type of thrombophilia.)
The deficiency was first described in a Norwegian patient in 1944. The incidence of Factor V deficiency is estimated at 1 per 1 million. It is usually inherited in an autosomal recessive fashion, which means it affects men and women equally. There are some case reports of a dominant pattern of inheritance in some families.
The role of the factor V protein is to be a catalyst or “accelerator” in the process by which prothrombin is converted to thrombin. Common characteristics of factor V deficiency are bruising, nose and mouth bleeds. Severe deep tissue bleeds are uncommon. Among people with severe forms of factor V deficiency, there can be joint bleeding and risks of head bleeds in newborns. Women can also present with menorrhagia.
Diagnosis is made through activated partial thromboplastin time (aPTT) test, prothrombin time (PT) test and thrombin clotting time (TCT) test. Diagnosis can be confirmed with a factor V assay. Factor V is found in both plasma and platelets, so platelets function may also be affected. A very rare condition, known as combined factor VIII and Factor V is characterized by more severe bleeding episodes. The combined FVIII+FV deficiency is a separate disorder that can be mistaken for either mild factor V or mild factor VIII deficiency.
There are no available factor V concentrates. Fresh frozen plasma (FFP) is the only treatment available. In acute cases of severe bleeding, the addition of platelet concentrates may be helpful. Depending upon availability, solvent-detergent FFP may contain a more reliable level of Factor V than standard FFP.