(Can also be 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 determined 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 is estimated at 1 in 500,000 births.  It 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 the deficiency, usually do not experience bleeding episodes, but do have bleeding after trauma or surgery.  Patients with severe forms of the disease, 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. 

Treatment

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.