Factor X deficiency is a disorder caused by too little of a protein called factor X in the blood. It leads to problems with blood clotting (coagulation).

When you bleed, the body launches a series of reactions that help the blood clot. This is called the coagulation cascade. The process involves special proteins called coagulation factors. (Factor X is a coagulation factor.) Each factor's reaction triggers the next reaction. The final product of the coagulation cascade is the blood clot. When certain coagulation factors are missing, the chain reaction does not take place normally.

Factor X deficiency is often caused by a defect of the factor X gene that is passed through families. This is called inherited factor X deficiency. Bleeding ranges from mild to severe.

Factor X deficiency may also develop due to another condition or use of medications. This is called aquired factor X deficiency. Acquired factor X deficiency is common. It may be caused by a lack of vitamin K, amyloidosis, severe liver disease, and use of drugs that prevent clotting (anticoagulants such as warfarin or coumadin). Some newborns are born with vitamin K deficiency. See: Vitamin k deficiency bleeding in newborns

Women with factor X deficiency may have very heavy menstrual bleeding and bleeding after delivery. Newborn boys with the condition may have longer-than-normal bleeding after circumcision.

Inherited factor X deficiency affects 1 out of every 500,000 people.