What Is Factor X Deficiency?

Factor X deficiency, also called Stuart-Prower factor deficiency, is a condition caused by not having enough of the protein known as factor X in your blood. Factor X plays a role in blood clotting, also called coagulation, which helps you to stop bleeding. Known as coagulation factors, several crucial proteins, including factor X, are involved in helping the blood to clot. If you are missing one or do not have enough, there is a greater chance that you will continue bleeding once you start.

The disorder may be passed down in families through genes (inherited factor X deficiency) but can also be caused by certain medications or another medical condition (acquired factor X deficiency). Inherited factor X deficiency cannot be cured. Treatment may involve getting transfusions to add clotting factors to your blood. To treat acquired factor X deficiency, your doctor will adjust or change your medication or address your underlying condition.

The outlook is generally good, but sometimes severe bleeding can occur.

Factor X deficiency can be mild or severe, depending on how much of the protein your blood contains.

Symptoms of mild factor X deficiency may include:

  • bruising easily
  • nosebleeds
  • bleeding from the mouth
  • excessive bleeding during or after trauma or surgery

More severe cases of the disorder often involve spontaneous episodes of both internal and external bleeding. Symptoms may include:

  • joint bleeding
  • muscle bleeding
  • gastrointestinal bleeding
  • hematomas (masses of clotted blood that form when a blood vessel breaks)

Very serious symptoms that are possible include:

  • spontaneous bleeding in the brain
  • bleeding into the spinal cord

Women with the deficiency may experience heavy bleeding during menstruation (periods). Factor X-deficient women who become pregnant are at high risk for miscarriage during the first trimester and severe bleeding during and after delivery.

Factor X Deficiency and Newborns

Babies born with inherited factor X deficiency may have symptoms such as excess bleeding at the site of the umbilical stump. Boys may bleed for longer than normal following circumcision. Some babies are born with a vitamin K deficiency, which may cause similar symptoms. This can usually be treated with a single vitamin K shot.

Factor X deficiency is generally classified by what causes it.

Inherited Factor X Deficiency

Inherited factor X deficiency is very rare. An inherited disorder is passed down from parents to children through genes. This type of factor X deficiency occurs when one of the genes is defective. The risk of parents giving it to their child is the same for both male and female children. The inherited type is estimated to occur in about one of every 500,000 people.

Acquired Factor X Deficiency

Acquired factor X deficiency is more common. You can get acquired factor X deficiency from a deficiency in vitamin K. Your body needs vitamin K to produce coagulation factors. Certain medications that inhibit clotting in the blood and blood vessels, such as warfarin or Coumadin, can also cause acquired factor X deficiency. These medications are called anticoagulants.

Other illnesses that may result in acquired factor X deficiency include severe liver disease and amyloidosis. Amyloidosis is a disorder in which abnormal protein buildup causes poor function in your tissues and organs. The cause of amyloidosis is unknown.

Factor X deficiency is diagnosed through a blood test called a factor X assay. The test measures the activity of factor X in your blood. Tell your doctor if you are taking any medications or have any other diseases or conditions before taking this test.

Your doctor may order other tests that are not specific to factor X but measure the time it takes for your blood to clot. These include:

  • prothrombin time (PT) test, which determines how long it takes plasma (the liquid part of blood) to clot. It measures the response of some of the coagulation factors, including factor X.
  • partial thromboplastin time, which also determines clotting time but measures the response of the other coagulation factors not covered by a PT test. The two tests are often done together.
  • thrombin time, which evaluates how long it takes for two specific coagulation factors (thrombin and fibrinogen) to interact and form a clot.

These tests are used to determine if your bleeding is caused by problems with clotting. They are often used in combination to monitor patients taking blood-thinning medications such as warfarin.

Managing and treating inherited factor X deficiency involves blood infusions of plasma or a concentrate of clotting factors.

In October 2015, the U.S. Food and Drug Administration approved a factor X concentrate called Coagadex. This drug is specifically meant to treat people who have inherited factor X deficiency. It is the first coagulation factor replacement therapy available, and it increases the limited treatment options that are available for people with this condition.

If you have acquired factor X deficiency, your doctor will design your treatment plan around the underlying condition that is causing the factor X deficiency.

Some conditions that cause factor X deficiency, such as a vitamin K deficiency, can be treated with vitamin supplements. Other conditions, such as amyloidosis, have no cure. The goal of your treatment is to manage your symptoms.

If the condition is caused by another disease, the outlook for acquired factor X deficiency will depend on treatment for that particular disease. People with amyloidosis may need surgery to take out their spleen.

In some cases, sudden or severe bleeding can occur despite treatment. Women who wish to become pregnant should be aware of the risks of miscarriage and severe bleeding during delivery and after the baby is born.