Factor X Deficiency

(Also known as Stuart-Prower Factor Deficiency.)

Factor X deficiency was first discovered in a man with the surname Stuart from North Carolina. While his doctors had originally thought he might have factor VII deficiency, a woman with the surname Prower was also noted to have the same clotting abnormality. Researchers realized that this was a new factor and called it the Stuart-Prower factor. It was later renamed Factor X deficiency.

The incidence of Factor X deficiency is estimated at 1 in 500,000 births. Factor X deficiency is inherited in an autosomal recessive fashion, which means it affects men and women equally.

The factor X protein activates the enzymes that help to form a clot. Several genetic variations of Factor X with varying degrees of severity have been described in the medical literature.


  • People with mild forms of Factor X deficiency usually do not experience bleeding episodes, but do have bleeding after trauma or surgery
  • Patients with severe forms of Factor X deficiency commonly have joint bleeding, gastrointestinal bleeds, and hematomas
  • Spontaneous head bleeds, spinal cord bleeds and bleeding at the site of the umbilical cord have also been reported
  • Women with Factor X deficiency may have menorrhagia or be susceptible to first trimester miscarriage


Diagnosis is made through a bleeding time test, prothrombin time (PT) test, and partial thromboplastin time (PTT) test. Diagnosis can be confirmed by a factor X assay, or a ruffle viper venom time assay.


There are no factor X concentrates available and fresh-frozen plasma is normally used as treatment. Prothrombin Complex concentrates (PCCs) have been used in patients, but it is important to know that the amount of factor X in each product in not consistent. There has also been a reported risk of thromboembolic complications with PCC product usage.