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Hemophilia B is a rare genetic bleeding disorder caused by insufficient levels of a blood protein called factor IX (or factor 9). It is the second most common type of hemophilia and occurs in approximately 1 in 25,000 male births.
Factor IX is a blood-clotting factor that promotes healing and helps the body seal wounds. Without it, the body struggles to effectively stop the flow of blood from a wound, injury, or bleeding site. As a result, people who have hemophilia B bruise easily and bleed for longer periods of time.
Other names for hemophilia B, include factor IX deficiency, Christmas disease, and the royal disease. The name "Christmas disease" is in honor of Stephen Christmas, the first person recorded in medical literature with the condition.
The name "the royal disease" stems from the most famous example of this hereditary condition being passed down from generation to generation. The family of Queen Victoria of England passed the disorder down to various descendants of the royal family, including members in Germany, Spain, and Russia.
This article will discuss the symptoms and causes of hemophilia B, as well as review the diagnostic process, treatment options, and disease prognosis.
Types of Hemophilia
There are many factors involved in the process of forming a blood clot. The type of hemophilia that you might have is based on which blood clotting factor you are deficient in. Insufficient levels of factor VIII, factor IX, and factor XI are most common.
The three main forms of hemophilia are:
- Hemophilia A: Caused by a deficiency of clotting factor VIII, this is the most common type, accounting for nearly 85% of all cases.
- Hemophilia B: Caused by a deficiency of clotting factor IX, this is the second most common type of hemophilia.
- Hemophilia C: Caused by a deficiency of clotting factor XI, this is the rarest type of hemophilia.
What Are the Symptoms?
Symptoms of hemophilia are largely dependent on the amount of factor IX (FIX) in your blood. Some people may not experience their first episode until adulthood, while others notice symptoms during infancy or childhood.
Early signs of hemophilia in infancy include:
- Bleeding into the muscle and deep bruising, sometimes first noticed after a routine vitamin K shot after birth
- Prolonged bleeding that goes on for a long time after the infant's heel is pricked to draw blood for newborn screening tests
- Prolonged bleeding after circumcision
- Bleeding in the scalp or brain after the use of a vacuum or forceps in delivery, or after a difficult delivery in general
Other general symptoms of hemophilia B include:
- Bleeding into a joint or muscle, which causes pain and swelling (hemarthrosis)
- Bleeding that is not normal after an injury or surgery
- Easy bruising
- Frequent nosebleeds
- Blood in the urine
- Bleeding after dental work
- Unexplained bleeding episodes
- Gastrointestinal (GI) tract and urinary tract bleeding
The symptoms of hemophilia B vary greatly from person to person. Generally, the higher your levels of FIX, the milder your symptoms will be. If FIX levels are between 6% and 49% of normal FIX in blood plasma, it is considered a mild case, and you are more likely to experience bleeding only after serious injury, trauma, or surgery.
In many cases, people with mild hemophilia B are unaware that they have the condition and only find out after an injury, surgery, or tooth extraction results in prolonged bleeding. Women with mild hemophilia often experience heavy menstrual periods (menorrhagia) and can hemorrhage after childbirth.
Even a small amount of FIX can stave off life-threatening bleeding episodes. Those with 1%–5% of FIX in the blood, or moderate hemophilia B, may have bleeding episodes after injuries or have spontaneous bleeding episodes.
If you have less than 1% of FIX in the blood you are at risk of life-threatening bleeding complications and are considered to have severe hemophilia B. People with severe hemophilia B experience bleeding following an injury and may have frequent spontaneous bleeding episodes, often into their joints and muscles.
Causes and Risk Factors
Hemophilia B is a hereditary disease. It primarily affects males, although female carriers of the disease may experience mild bleeding symptoms due to reduced levels of factor IX (FIX) in the blood.
Hemophilia B is caused by defects in the F9 gene located on the X chromosome. The F9 gene is just one gene involved in the blood-clotting process. It is responsible for manufacturing and activating factor IX. Mutations in the F9 gene are inherited 70% of the time and arise spontaneously 30% of the time.
Hemophilia B is an X-linked inherited condition, which means that transmission of the disease is linked to the carrier status of the mother. A mother who carries the gene for hemophilia has a 50% chance of transmitting the gene in each pregnancy. Males who inherit the pathogenic variant will be affected, while daughters who inherit the pathogenic variant will be carriers.
A male who has hemophilia B will pass down the gene for the disease to all of his daughters and none of his sons because males receive his Y chromosome. A female who has the condition (or is a carrier) will pass the gene to approximately half of her offspring—whether they are male or female.
Most people have the genetic or inherited form of hemophilia B, but there is another rare form of hemophilia B that can be acquired with age. This nonhereditary form of hemophilia B can develop if the body starts to produce antibodies against its own factor IX protein. The reasons why this happens in rare instances are unknown.
How Hemophilia B Is Diagnosed
A diagnosis of hemophilia B is made after your healthcare provider takes a detailed history of your bleeding episodes, a family history of bleeding and inheritance, and laboratory testing. Specialized blood coagulation tests are needed to confirm the diagnosis.
Blood tests are used to measure how long it takes your blood to form a clot. Laboratory studies for suspected hemophilia B include a complete blood cell count, coagulation studies, and a factor IX (FIX) assay.
The following FIX levels denote severity (levels calculated by the percent of FIX in blood plasma):
- Mild: Greater than 5%–49% of normal
- Moderate: 1%–5% of normal
- Severe: Less than 1% of normal
Genetic testing to look for the specific mutation in the F9 gene responsible for hemophilia B may also be performed to confirm the diagnosis.
What Are the Treatment Options?
There is no cure for hemophilia B, but it’s possible for people with hemophilia and their families to learn how to prevent injury and give their own clotting-factor treatment products at home.
The main treatment of hemophilia B involves prophylaxis (avoiding injury), having a plan to manage bleeding episodes, and replacement therapy of factor IX. There are two types of clotting factor concentrates that may be given intravenously (via IV, intravenously).
- Plasma-derived factor concentrates: Freeze-dried blood-clotting factors from human plasma
- Recombinant factor concentrates: Reengineered plasma factors that do not contain human plasma or albumin
Hemophilia treatments are often given at a comprehensive hemophilia treatment center (HTC). These specialized units consist of a multidisciplinary team that includes doctors who specialize in the treatment of blood disorders called hematologists as well as healthcare providers who specialize in physical medicine and rehabilitation for people with bleeding disorders, including nurses, social workers, and physical therapists.
Prognosis of Hemophilia B
Until 1970, the life expectancy for a person with all types of hemophilia was about 12 years old, but thanks to advances in medical therapies and better access to care, hemophilia B has become a largely chronic disease that many people can adequately manage throughout their life.
The life expectancy of someone with hemophilia is still about 10 years less than a person without hemophilia, but ultimately life expectancy and the risk of having a medical complication are dependent on the severity of your disease, access to care, and whether you have other medical conditions.
Hemophilia B is a hereditary condition that can cause minor and major bleeding episodes. The condition is due to a deficiency in blood-clotting factor called factor IX.
This condition can be diagnosed with blood tests. You or your child may also have genetic testing done for the gene mutation that causes hemophilia B as part of the diagnostic process.
While there is no cure for hemophilia B, there are treatments available (such as factor IX replacements) that can help reduce the severity and frequency of bleeding episodes and improve your quality of life. Living with hemophilia B may mean you need to take care to avoid injuries, but it is possible to live a healthy, normal lifespan with the condition.
A Word From Verywell
Medical advances have made it possible for people with hemophilia B to live full and productive lives. Some people with hemophilia experience frequent bleeding episodes, while others experience very few.
No matter where you fall on the spectrum, combining the three approaches of avoiding injuries, prompt management of even minor injuries, and replenishing your clotting factors is a safe and effective way to lessen the likelihood of having a serious bleeding episode and other complications.