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Hemophilia B

Definition

Hemophilia B is a hereditary blood coagulation disorder. It is caused by a deficiency of a blood plasma protein called factor IX that affects the clotting property of blood.

Alternative Names

Christmas disease; Factor IX hemophilia

Causes, incidence, and risk factors

Hemophilia is a hereditary bleeding disorder of specific blood clotting factors. There are several types of hemophilia, including hemophilia A and B. Hemophilia A is 7 times more common than hemophilia B. Hemophilia B is the result of a deficiency of clotting factor IX.

The disorder is caused by an inherited X-linked recessive trait, with the defective gene located on the X chromosome. Thus, the disorder occurs primarily in males. Females carry two copies of the X chromosome, so if the factor IX gene on one chromosome is defective, the other can compensate. Males, however, carry only one X chromosome, so if the factor IX gene on that chromosome is defective, they have the disease.

Females with one defective factor IX gene are carriers of this trait. Half of the male babies born from women who carry the defective gene have a 50% chance of developing the disease. Half of the female babies born from women who have the defective gene have a 50% chance of being carriers.

The severity of symptoms can vary with this disease, and the severe forms become apparent early on. Bleeding is the hallmark of the disease and sometimes, though not always, occurs if an infant is circumcised. Additional bleeding manifestations make their appearance when the infant becomes mobile.

Mild cases may go unnoticed until later in life, when they occur in response to surgery or trauma. Internal bleeding may occur anywhere and bleeding into joints is common. Risk factors are a family history of bleeding and being male. Hemophilia B occurs in about 1 out of 32,000 men.

Symptoms

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

Signs and tests

Coagulation studies involving many tests are performed if the person tested is the first one in the family to have a bleeding disorder. Once the defect has been identified, other family members will need less testing to diagnose the disorder.

Treatment

Standard treatment is infusion of factor IX concentrates to replace the defective clotting factor. The amount infused depends upon the severity of bleeding, the site of the bleeding, and the size of the patient. Hepatitis B vaccine is recommended for individuals with Hemophilia B because they are at increased risk of developing hepatitis due to exposure to blood products.

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 regular prophylactic infusions.

Depending on the severity of the disease, factor IX concentrate may be given prior to dental extractions and surgery to prevent bleeding.

Support Groups

For additional information, see hemophilia support group.

Expectations (prognosis)

The outcome is usually good with treatment. Most people with hemophilia are able to lead relatively normal lives. A small percentage of people develop inhibitors of factor IX, and may die from loss of blood.

Complications

Calling your health care provider

  • Call your health care provider if symptoms of a bleeding disorder develop.
  • Call for an appointment with your health care provider (for screening) if a family member has been diagnosed with hemophilia B.
  • Call for an appointment with your health care provider if you have hemophilia B, and you plan to have children.

Prevention

Genetic counseling may be advised. Female carriers can be identified by testing.

Review Date:1/14/2008
Reviewed By:David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc. Previously reviewed by William Matsui, MD, Assistant Professor of Oncology, Division of Hematologic Malignancies, The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Baltimore, MD. Review provided by VeriMed Healthcare Network (5/3/2006).

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