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What is hemophilia B?
Hemophilia B is a rare bleeding disorder that prevents the body from effectively stopping bleeding. It is caused by a deficiency or absence of factor IX, a protein that plays a key role in the blood clotting process.
When a person with hemophilia B is injured, the blood takes longer to clot, which can lead to prolonged or spontaneous bleeding.
Like hemophilia A, hemophilia B is a genetic inherited disorder linked to the X chromosome. It mainly affects men, while women are most often carriers of the genetic mutation.
This form of hemophilia is less common than hemophilia A and accounts for around 15 to 20% of hemophilia cases.
What are the symptoms of hemophilia B?
The symptoms of hemophilia B are similar to those seen in hemophilia A. Their severity usually depends on the level of factor IX present in the blood.
Prolonged bleeding
People with hemophilia B may experience prolonged bleeding after an injury, surgery, or dental procedure.
In some cases, bleeding can also occur spontaneously, without any obvious trauma.
Frequent bruising
Bruises or hematomas may appear easily, sometimes after minor injuries. These bruises may be larger than those seen in people without a bleeding disorder.
Bleeding in the joints
One of the characteristic signs of hemophilia is the occurrence of hemarthroses, which are bleeds inside the joints.
These bleeds most often affect the knees, elbows, or ankles. They can cause pain, swelling, and reduced mobility. When they occur repeatedly, they may lead to long-term joint damage.
How is hemophilia B diagnosed?
The diagnosis of hemophilia B is based on blood tests that evaluate how the clotting system functions.
Clotting tests
When doctors suspect a bleeding disorder, blood tests are carried out to assess the time needed for a clot to form.
These tests help identify abnormalities in the clotting process.
Factor IX measurement
The diagnosis is confirmed by measuring factor IX levels in the blood. A low or absent level of this factor allows hemophilia B to be identified and its severity to be determined.
Depending on the amount of factor IX present, the condition may be classified as mild, moderate, or severe.
Genetic testing
In some cases, genetic testing may be offered to identify the mutation responsible for the disorder. This can also help detect women who carry the mutation within a family.
What are the treatments for hemophilia B?
Treatment for hemophilia B aims to replace or compensate for the missing factor IX in order to prevent or control bleeding episodes.
Replacement therapy
The main treatment involves the administration of factor IX concentrates. These treatments temporarily restore sufficient clotting ability to stop bleeding or prevent it from occurring.
Factor IX may be administered during a bleeding episode or regularly as part of preventive treatment known as prophylaxis.
Preventive treatments
Prophylaxis involves regular administration of factor IX in order to maintain sufficient clotting levels and reduce the risk of bleeding, particularly in the joints.
This approach helps improve quality of life and limit joint complications.
New therapeutic approaches
Advances in research have led to the development of new therapeutic approaches, including extended half-life treatments and ongoing research into gene therapy.
These innovations aim to reduce the frequency of injections and improve disease control.
Living with hemophilia B
Thanks to advances in treatment and appropriate medical follow-up, people with hemophilia B can now lead active lives.
Regular follow-up in specialized centers helps adapt treatment, prevent complications, and support patients in their daily lives.
Care often involves a multidisciplinary approach including hematologists, physical therapists, and other healthcare professionals in order to provide comprehensive management of the condition.
Last updated: 3/10/26
