People with factor X (10) deficiency (sometimes called Stuart-Prower deficiency) have low levels of factor X in their blood. Factor X helps activate a protein called prothrombin (factor II), which is needed to form a stable blood clot.

Recently, an international organization (International Society on Thrombosis and Hemostasis) proposed a classification of factor X deficiency severity based upon factor activity and associated symptoms, with a few exceptions.

• Mild (> 40% activity): Patients are mostly asymptomatic, but might have problems with bleeding during trauma, a surgical procedure or with pregnancy/delivery
• Moderate (10-40% activity): Patients may have mild spontaneous bleeding, or bleeding triggered by trauma, surgery, or pregnancy/delivery
• Severe (< 10% activity): Patients may have spontaneous, severe, and even life-threatening bleeding

Factor X deficiency is inherited from both parents. It can also develop as a person gets older. It is rare and occurs in 1 in every 500,000 to 1 million people.

The level of factor X in the blood does not always match the severity of bleeding. Symptoms include:

• Umbilical stump bleeding at birth (for those severely affected)
• Nose bleeds
• Mouth bleeds
• Easy bruising
• Swelling, pain, or warmth around a joint
• Inability to straighten or bend a joint normally
• Headache or neck ache
• Drowsiness or loss of consciousness
• Upset stomach
• Vomit that is black and syrupy or bright red
• Sensitivity to light
• Weakness, tingling, or pain in the arms or legs
• Difficulty with urination or bowel movements
• Bleeding after surgery or trauma
• In women, heavy menstrual bleeding

Factor X deficiency is diagnosed after finding screening tests that identify prolonged prothrombin time (PT) and activated partial thromboplastin time (aPTT) then by following up to determine that factor X activity is lower than normal. These results should be confirmed by a specialized health care provider.

Bleeding episodes may need to be treated. There are blood-derived products that include factor X but no specific factor concentrates are available. Excessive menstrual bleeding in women with factor X deficiency may be controlled with hormonal contraceptives (birth control pills), intra-uterine devices (IUDs), or antifibrinolytic drugs.