Factor XI deficiency is a rare, inherited bleeding disorder. XI means “eleven” in Roman numerals. If you have factor XI deficiency, your blood doesn’t clot properly because it lacks certain proteins called “clotting factors.”

Factor XI deficiency is sometimes called hemophilia C and is a relatively mild form of hemophilia. If you have factor XI deficiency, you might experience heavy menstrual periods, or bleeding after surgeries, such as dental extractions.

Though there is no cure, treatments are available to help minimize symptoms and prevent future health problems.

Factor XI deficiency is a rare bleeding disorder. People with Factor XI deficiency don’t have enough of a protein in the blood called factor XI.

Factor XI is a clotting factor. Factor XI is one of a few clotting factors in blood that helps with the clotting process to control bleeding. Clotting is a process in the body by which blood solidifies to seal a wound in order to stop bleeding.

With a shortage of factor XI in the blood, you might experience excessive bleeding when you’re injured or undergoing a surgical procedure. You won’t bleed any faster than people without factor XI deficiency, but it may be more difficult to stop blood flow from a deep wound or surgery.

Factor XI deficiency is rare. It’s estimated to occur in just 1 in every 100,000 people.

Factor XI deficiency might also be called other names, including:

  • factor 11 deficiency
  • hemophilia C
  • haemophilia C
  • PTA deficiency
  • plasma thromboplastin antecedent deficiency
  • Rosenthal syndrome

The symptoms of factor XI deficiency tend to be mild compared to other types of hemophilia. There’s a good chance you won’t experience any symptoms at all.

If you do experience symptoms, they may include:

Bleeding risk varies from person to person.

The primary cause of factor XI deficiency is an abnormal change, called a mutation, in the genes that regulate the formation of clotting factors in the blood. Clotting factors help form clots and close bleeding wounds caused by injuries, accidents, and surgeries.

If you have a mutation, the gene responsible for giving the instructions to your body to make factor XI won’t be able to do so properly. This abnormal gene may not make enough factor XI or may not make factor XI at all. This results in a shortage of factor XI in the body.

Factor XI deficiency is an inherited condition. This means that the mutation responsible for this condition is passed down from parents to children.

The mutation responsible for factor XI is autosomal recessive. It’s not linked to the sex chromosomes. To get factor XI deficiency from your parents, both parents need to have at least one copy of the factor XI mutation.

If you carry one copy of the mutation for factor XI deficiency, you’re considered a carrier. Carriers may have slightly lower than average factor XI levels, but typically don’t have noticeable symptoms. You can only pass on the condition to your children if your partner also carries the mutation.

In rare cases, you can develop factor XI deficiency later in life. For example, it can be caused by severe liver disease since factor XI is produced in the liver, or it may be caused if you receive a liver transplant from someone affected by factor XI deficiency. This is called acquired factor XI deficiency.

Your doctor will likely ask you if you have a family history of bleeding disorders and ask about your symptoms and any medications you’re currently taking.

Factor XI deficiency can be diagnosed with blood tests. To perform these tests, a phlebotomist or nurse will take a small sample of blood by inserting a needle into a vein on the inside of your elbow. Tests may include:

  • Bleeding time test: A bleeding time test measures how long it takes for your blood to form clots to stop bleeding.
  • Platelet function tests: These are a group of tests that evaluate the function of your platelets. Platelets are pieces of cells from the bone marrow that are important in forming blood clots.
  • Prothrombin time test (PT) and activated partial thromboplastin time (aPTT) test: Prothrombin time (PT) and activated partial thromboplastin time (aPTT) tests measure the amount of time it takes for your blood plasma to clot.
  • FXI assay to confirm the diagnosis: This test can find out if your body produces enough of this specific clotting factor.

Most people with factor XI deficiency don’t require treatment. If you are injured or in an accident, you might need to receive fresh frozen plasma (FFP) dripped into a vein (intravenously) to replace some of the lost clotting factors.

Your doctor may also recommend that you take medications for factor XI deficiency to help prevent bleeding before a planned surgery or if you’re having a baby.

For minor surgeries, your doctor may prescribe tranexamic acid or aminocaproic acid tablets to take beforehand and for a few days afterward. These medications work by slowing down the breakdown of clotting factors in the blood. For major surgeries, you may need to receive FFP.

If you’re experiencing very heavy periods caused by factor XI deficiency, a doctor may suggest that you take tranexamic acid tablets during your periods. Oral contraceptive pills (birth control pills) can also help make your periods lighter.

You should avoid taking nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen or aspirin, before or after surgery. These medications may increase your risk of bleeding.

Factor XI deficiency occurs equally in people assigned male or female at birth.

In general, you’re at a higher risk of having factor XI deficiency if:

Factor XI deficiency is considered manageable, especially when compared to other bleeding disorders. Most people can expect to live a normal life.

People with factor XI deficiency don’t tend to bleed spontaneously like in other types of bleeding disorders. Bleeding is most frequently seen after surgery or trauma. With treatment or preventive therapy (prophylaxis), people with factor XI deficiency can undergo surgeries safely.

Here are answers to some frequently asked questions about factor XI deficiency.

What’s the difference between factor XI, factor VIII, and factor IX deficiency?

There are many types of clotting factors in the body. The main difference between factor VIII deficiency (hemophilia A), factor IX deficiency (hemophilia B), and factor XI deficiency is the type of clotting factor that your body lacks.

In general, the symptoms of factor XI and VIII deficiency tend to be more serious than the symptoms of factor XI deficiency and the risk of bleeding is much higher.

How many people have factor XI deficiency in the United States?

Factor XI deficiency is rare and some people can have the condition without knowing they have it. The National Institutes of Health (NIH) estimates that between 300 and 3,000 people are currently living in the United States with this factor XI deficiency.

Should I tell my dentist if I have factor XI deficiency?

You should tell your dentist or oral surgeon if you know you have factor XI deficiency, You may need to take medications or take precautions before any dental procedures, especially surgeries, to minimize the risk of bleeding.

Some people don’t find out that they have factor XI deficiency until after they’ve experienced higher than normal bleeding after a dental procedure. If you bleed a lot during dental work, talk with your doctor about getting tested for factor deficiency.

If I have factor XI deficiency but my partner does not, will my kids have it too?

Factor XI deficiency is a recessive inherited disorder. This means that both parents need to have at least one copy of the abnormal gene responsible for the disorder to pass it down to their children. If you have factor XI deficiency, but your partner doesn’t have any copies of the abnormal gene, your children will not have factor XI deficiency but will be carriers of the disorder.

However, if your partner is a carrier (one copy of the abnormal gene), your kids only have a 50% likelihood of having factor XI deficiency and a 50% chance of being a carrier of the disorder.

Does factor XI deficiency ever go away?

Though plasma transfusions and medications can help treat or prevent bleeding, factor XI deficiency is considered a lifelong condition with no cure. You also can’t prevent factor XI deficiency because it’s an inherited condition.

Factor IX deficiency is a bleeding disorder that can make it difficult for your body to clot properly following an injury or surgery. Symptoms are usually mild.

If you have factor IX deficiency, it’s important to talk with your doctor about the need for medications or plasma infusions before an operation, during menstruation, or during childbirth.

If you plan to have children, pre-conception and prenatal counseling can also help you understand the chances of passing this disorder to your kids.