Hemophilia B; Factor IX hemophilia
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
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. Fifty percent of the male offspring of female carriers will have the disease, and 50% of their female offspring will be carriers. All female children of a male hemophiliac will be carriers of the trait.
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.
- 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.
- PTT is prolonged.
- Prothrombin time is normal.
- Bleeding time is normal.
- Fibrinogen level is normal.
- Serum factor IX is reduced.
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.
For additional information, see hemophilia support group.
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.
- Chronic joint deformities, caused by recurrent bleeding into the joint, may be managed by an orthopedic specialist.
- Recurrent transfusions may expose the individual to HIV and hepatitis, especially prior to 1985 when blood screening procedures were improved for detecting the HIV virus.
- Intracerebral hemorrhage (such as deep intracerebral hemorrhage and lobar intracerebral hemorrhage) may also occur.
- Thrombosis may occur following use of factor IX concentrate.
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.
Genetic counseling may be advised. Female carriers can be identified by testing.
by Sharon M. Smith, M.D.
All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.