Factor X deficiency is a condition caused by not enough of the protein factor X in your blood. This coagulation factor is important for clotting, so a deficiency increases the risk of excessive bleeding.

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Factor X deficiency is also called Stuart-Prower factor deficiency.

There are two types:

  • inherited factor X deficiency, which can pass down to you genetically
  • acquired factor X deficiency, which you can get from taking certain medications or another underlying condition

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:

  • bleeding in the brain, or intracranial hemorrhage
  • bleeding in the lungs, or pulmonary hemorrhage
  • bleeding in the spinal cord

People assigned female at birth (AFAB) with the deficiency may experience heavy bleeding during menstruation (periods). Those 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.

Male newborns may bleed for longer than normal following circumcision. This is usually caused by a vitamin K deficiency and be treated with a single vitamin K shot.

[the terms “male” and “female”]

In this article, we use “male and female” to refer to someone’s sex as determined by their chromosomes, and “men and women” when referring to their gender (unless quoting from sources using nonspecific language).

Sex is determined by chromosomes, and gender is a social construct that can vary between time periods and cultures. Both of these aspects are acknowledged to exist on a spectrum both historically and by modern scientific consensus.

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Factor X deficiency is generally classified by what causes it.

Inherited Factor X Deficiency

Inherited factor X deficiency is rare, with an incidence rate of about 1 in 500,000 to 1 in a million.

It is an inherited disorder passed down from parents to children through genes. It is caused by changes to the F10 gene, which is responsible for producing the factor X protein.

This protein is a vital part of normal blood clotting. Mutations can either reduce the amount of this protein in circulation (type I) or impair its ability to work as it should (type II). Either way, not enough working factor X can lead to uncontrolled bleeding and other life threatening issues.

The risk of parents giving it to their child is the same for children of either sex.

Acquired Factor X Deficiency

You can develop acquired factor X deficiency from various conditions, and the incidence depends on the underlying cause. That said, it is still a rare disorder.

Conditions that can cause factor X deficiency include:

You can also get it by taking anticoagulant medications like thrombin or warfarin (Jantoven).

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

For minor bleeding, your doctor may prescribe tranexamic acid, which can help control the bleeding.

Other treatments for the hereditary form may include plasma infusion or injection of prothrombin, which counteracts the effects of anticoagulants.

In October 2015, the Food and Drug Administration (FDA) also approved a factor X concentrate called Coagadex for people with 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 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.

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 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 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 problems with clotting are causing your bleeding. They are often used in combination to monitor patients taking blood-thinning medications such as warfarin.

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

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