Hemophilia B (Christmas Disease): What is It?

Even though it's called "Christmas disease," Hemophilia B is not related to the popular holiday. Hemophilia B is a rare blood disorder. It causes your blood not to clot properly because of a missing or defective protein called factor IX.

Key takeaways:
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    Christmas disease, or hemophilia B is a rare blood disorder that causes improper blood clotting.
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    Most cases of hemophilia B are passed down from parents to children, but about one-third of cases are caused by a genetic mutation.
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    Hemophilia B requires a screening and clotting test to be diagnosed.
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    It’s possible to live a healthy and happy life with Christmas disease with the right maintenance and care.

Christmas disease is also called factor IX hemophilia and hemophilia B. It is named after Stephen Christmas, who was the first person to be diagnosed with it in 1952.

According to the National Hemophilia Foundation, most people with hemophilia B have inherited it. It can affect all races and ethnicities but mainly occurs in males or people with XY chromosomes.

What are the causes of Hemophilia B?

Over 60% of Christmas disease cases are genetic and are passed down from parent to child. However, approximately one third of cases come from a gene mutation that can cause problems with factor IX, a clotting protein needed for proper blood clotting.

Hemophilia B symptoms

People with Christmas disease tend to bleed more than others, and the bleeding is usually internal. How often and how badly a person bleeds depends on how much factor IX, also known as FIX or Christmas factor, is in the person’s plasma. Plasma is the mildly yellow, fluid part of the blood.

Normal plasma FIX blood levels are 50-150 percent. Below 50 percent is when blood is no longer able to clot, which is when symptoms begin to show up.

The lower the FIX levels, the more hemophilia B symptoms appear:

Mild hemophilia B. People with 6-49 percent of FIX in the blood have mild forms of hemophilia B. This means they mainly only experience internal bleeding after serious injury, trauma or surgery.

Moderate hemophilia B describes people with 1-5 percent of FIX in the blood. People with moderate hemophilia B tend to have bleeding episodes after injuries, but can also experience some bleeding without injury, called spontaneous bleeding episodes.

Severe hemophilia B includes people with less than one percent of FIX in the blood. These people experience bleeding after injuries, but also have frequent spontaneous bleeding episodes.

How is Hemophilia B inherited?

Christmas disease is inherited through the X chromosome.

Most females get one X chromosome from their mother and one from their father (XX). Males typically get one X chromosome from their mother and one Y chromosome from their father.

Since hemophilia B is a recessive gene, females can be carriers of the hemophilia B gene, but often do not get the disease due to another healthy X chromosome that cancels out the gene’s effects.

People at higher risk of hemophilia B have XY chromosomes, because there is no healthy X chromosome to block the effects of the hemophilia B gene.

Diagnosis of Hemophilia B

Many families with a history of hemophilia B choose to have their children tested early on. To be diagnosed with hemophilia B requires both a screening test and a clotting test.

Screening tests show if the blood is clotting properly. If not, then a clotting test is given to determine the hemophilia type and severity (mild, moderate, or severe).

Since about 30 percent of all Christmas disease cases are not passed down from parents, there are a few cases that may encourage a doctor to test for the disease:

  • If bleeding after a circumcision continues for longer than normal.
  • When someone continues to bleed after drawing blood.
  • If there is bleeding in the head or scalp after infant surgery.
  • When someone has an unusually large amount of bruises.

Hemophilia A vs B: What is the difference?

Hemophilia A and B are both caused by blood that doesn't clot properly because a protein is missing or defective. However, the type of protein that causes the issue in both types is different.

Hemophilia B is caused by a lack of factor IX. In hemophilia A, also known as classic hemophilia and royal disease, blood clot issues are caused by not having enough of factor VIII.

Hemophilia A is much more common than hemophilia B, though the symptoms are very similar.

Hemophilia B treatment

The main way to treat hemophilia B is to replace factor IX so that the blood can clot properly. Doctors typically use a concentrated FIX product called "clotting factor" or "just factor" to do this.

Depending on how active their factor IX is, hemophilia carriers who do not usually experience symptoms of the disease may need FIX replacement therapy after giving birth or before dental or surgical procedures to stop bleeding.

How to live with Hemophilia B

Living with Christmas disease can be challenging, especially for those with more severe symptoms. With the right treatment and care, though, it is possible to live a happy and normal life.


There are no specific diet requirements for people with Christmas disease, but they can benefit from eating certain foods and avoiding others. For example, experts recommend an iron-rich diet, which includes lean red meat, poultry, and leafy green vegetables like broccoli.

It’s also recommended that people with hemophilia B consult a doctor before taking certain supplements like vitamin E and fish oil. These supplements might increase bleeding.


Even though it's not always possible to avoid getting hurt from exercise, the benefits of being active far outweigh the risks for people with hemophilia B. In fact, exercise can help lower the risk of spontaneous bleeding by making muscles and joints stronger.

Preventative measures

There are about 100 hemophilia treatment centers (HTCs) across the United States and Canada. HTCs allow people with hemophilia B to receive all of their specialized care in one location.

Studies show that people with hemophilia who get care at an HTC have better long-term health and are less likely to die early from their condition.


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