Hemophilia B

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X-linked recessive genetic defects - how boys are affected

X-linked recessive genetic defects - how girls are affected

X-linked recessive genetic defects

Blood cells

Blood clots

Definition

Hemophilia B is a hereditary bleeding disorder caused by a lack of blood clotting factor IX. Without enough factor IX, the blood cannot clot properly to control bleeding.

See also: Coagulation disorder

Alternative Names

Christmas disease; Factor IX hemophilia

Causes, incidence, and risk factors

Hemophilia B is caused by an inherited X-linked recessive trait, with the defective gene located on the X chromosome.

Females have two copies of the X chromosome. If the factor IX gene on one chromosome is defective, the gene on the other chromosome can do the job of making enough factor IX.

Males have only one X chromosome. If the factor IX gene is missing on a boy's X chromosome, he will have Hemophilia B. Most people with hemophilia B are male.

If a woman has a defective factor IX gene, she is considered a carrier. This means the defective gene can be passed down to her children. Boys born to such women have a 50% chance of having hemophilia B. Their daughters have a 50% chance of being a carrier.

All female children of men with hemophilia carry the defective gene.

Risk factors for hemophilia B include:

• Family history of bleeding
• Being male

References

Alternative Names

Christmas disease; Factor IX hemophilia

Symptoms

The severity of symptoms can vary, and the severe forms become apparent early on.

Bleeding is the main symptom. It is often first seen when the an infant is circumcised. Additional bleeding problems usually show up when the infant starts crawling and walking.

Mild cases may go unnoticed until later in life. Symptoms may first occur after surgery or injury. ur in response to surgery. Internal bleeding may occur anywhere.

Symptoms can include:

• Bleeding into joints and associated pain and swelling
• Blood in the urine or stool
• Bruising
• Excessive bleeding following circumcision
• Gastrointestinal tract and urinary tract hemorrhage
• Nosebleeds
• Prolonged bleeding from cuts, tooth extraction, and surgery
• Spontaneous bleeding

Signs and tests

If you are the first person in the family to have a suspected bleeding disorder, your doctor will order a series of tests called a coagulation study. Once the specific defect has been identified, other people in your family will need tests to diagnose the disorder.

Blood tests results may include:

• Partial thromboplastin time (PTT)
• Normal Prothrombin time
• Normal Bleeding time
• Normal Fibrinogen level
• Low Factor IX

References

Alternative Names

Christmas disease; Factor IX hemophilia

Treatment

Treatment includes replacing the defective clotting factor. You will receive factor IX concentrates. How much you get depends on:

• Severity of bleeding
• Site of bleeding
• Your weight and height

To prevent a bleeding crisis, people with hemophilia and their families can be taught to administer factor IX concentrates at home at the first signs of bleeding. People with severe forms of the disease may need ongoing, preventive infusions.

If you have severe hemophilia, you may also need to take factor IX concentrate before surgery or certain types of dental work.

You should get the Hepatitis B vaccine. People with hemophilia are more likely to get hepatitis because they may receive blood products.

Expectations (prognosis)

With treatment, most people with hemophilia are able to lead relatively normal lives. However, death from extreme blood loss can occur.

If you have hemophilia, you should have regular check ups with a hematologist.

Complications

Complications can include :

• Long-term joint problems, which may require a joint replacement
• Bleeding in the brain (intracerebral hemorrhage)
• Thrombosis due to treatment

Repeated transfusions may slightly raise the risk for HIV and hepatitis. However, continued improvements in blood screening procedures makes blood products safer than ever.

Calling your health care provider

Call your health care provider if:

• Symptoms of a bleeding disorder develop
• A family member has been diagnosed with hemophilia B
• If you have hemophilia B, and you plan to have children; genetic counseling is available

References

Alternative Names

Christmas disease; Factor IX hemophilia

Prevention

Genetic counseling may be recommended. Testing can identify women and girls who carry the hemophilia gene.

Testing can be done during pregancy on a baby that is in the mother's womb.

References