Blood Home > Hemophilia B

Hemophilia B is a type of bleeding disorder in which blood does not clot as it should. Also known as Christmas disease, it is caused by a mutation in the F9 gene. People with this condition have a partial or complete lack of clotting factor 9 (IX). Common symptoms include bleeding and bruising, and treatment typically involves replacing the missing clotting factor.

What Is Hemophilia B?

Hemophilia is a rare, inherited bleeding disorder in which the blood does not clot normally. People with the condition may bleed for a longer time following an injury or accident. They may also bleed internally, especially in the joints such as the knees, ankles, and elbows.
A person with hemophilia has a problem with certain proteins in the blood, called clotting factors, that help blood clot. The disorder can be due to a low level of one of the clotting factors or a clotting factor that is completely missing.
When clotting factors are missing, or when the body does not have enough clotting factors, it can take a long time for blood to clot after an injury or accident.
Approximately 18,000 people in the United States have hemophilia, and about 400 U.S. babies are born each year with this disorder. The condition usually occurs only in males; however, there are rare exceptions in which hemophilia will occur in a female.
There are two main types:
Hemophilia B is also known as Christmas disease. Approximately 1 out of 10 people with hemophilia have type B.
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Last reviewed by: Arthur Schoenstadt, MD
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