(Can also be known as Stuart-Prower Factor Deficiency)
In the late 1950s, factor X deficiency was identified in a man with the surname Stuart from North Carolina. While his doctors had initially thought he might have factor VII deficiency, a woman with the surname Prower was found to also have the same bleeding abnormality. Researchers subsequently determined that this was a new inherited factor disorder and it was known as the “Stuart-Prower factor” until renamed “Factor X Deficiency” in 1962.
The worldwide incidence of inherited Factor X is estimated at 1 in 500,000-1,000,000 individuals. This rare bleeding disorder is inherited in an autosomal recessive fashion, which means it affects men and women equally. The factor X protein plays an important role in activating the enzymes that help to form a clot. Several genetic variations of Factor X with varying degrees of severity have been reported in the medical literature.
Diagnosis is made through family history, prothrombin time (PT) test, partial thromboplastin time (PTT) or activated partial thromboplastin time (APTT) test. Diagnosis can be confirmed by a factor X functional activity (FX:C) or the Russell viper venom (RVV) time assay
People with the mild form of Factor X deficiency, do not usually experience spontaneous bleeding episodes, but more commonly have easy bruising, nose or mouth bleeds and bleeding after trauma or surgery. Patients with severe forms of this deficiency, tend to experience joint bleeding, gastrointestinal bleeds, and hematomas. More serious events such as spontaneous head bleeds, spinal cord bleeds and bleeding at the site of the umbilical cord have also been reported in the literature. Women with factor X deficiency may experience heavy menstrual bleeding (menorrhagia), be susceptible to first trimester miscarriage or other complications during pregnancy and delivery. Patients with severe factor X deficiency, especially those who may require surgery should consult with a hematologist at a Hemophilia Treatment Center.
There is no factor X concentrate currently available in the US. Fresh-frozen plasma or plasma-derived Prothrombin Complex concentrates (PCCs) are normally used as treatment. PCCs lessen the risk of viral transmission since they undergo a step of viral inactivation, but it is important to know that the amount of factor X in each product in not consistent.
In patients with mild deficiency, antifibrinolytic agents (ex. Aminocaproic acid or tranexamic acid) or topical therapies (such as nosebleed powders or fibrin glue) may relieve bleeding symptoms.