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X-linked recessive genetic defects - how boys are affected
X-linked recessive genetic defects - how boys are affected

X-linked recessive genetic defects - how girls are affected
X-linked recessive genetic defects - how girls are affected

X-linked recessive genetic defects
X-linked recessive genetic defects

Blood cells
Blood cells

Blood clots
Blood clots


Hemophilia B is a hereditary blood coagulation disorder . It is caused by a deficiency of a blood plasma protein called factor IX. Without enough factor IX, the blood cannot clot properly to control bleeding.

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. Females have two copies of the X chromosome, so if the factor IX gene on one chromosome is defective, the other can compensate. Males, however, have only one X chromosome, so if the factor IX gene on that chromosome is defective, they will have the disease. Thus, more males than females have hemophilia.

Females with one defective factor IX gene are carriers of (they don't have symptoms). In women who are carriers, their male babies have a 50% chance of having the disease, while their female babies have a 50% chance of being a carrier.

The severity of symptoms can vary, and the severe forms become apparent early on. Bleeding is the main symptom of the disease and sometimes, though not always, occurs if an infant is circumcised. Additional bleeding problems usually show up 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.

  • 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 your family to have a bleeding disorder, you will undergo a series of tests called a coagulation study. Once the specific defect has been identified, other family members will need less testing to diagnose the disorder.


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 ongoing, preventive 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.

People with hemophilia B should establish an ongoing relationship with a hematologist, especially one associated with a hemophilia treatment center. The ability to have quick and easy access to medical records describing their level of Factor IX, history of transfusions (including the type and amount), any complications they've had, and the type and amount of any inhibitors can be lifesaving in the event the person with hemophilia is in an emergency situation.


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.

References: Roberts HR, et al. Hemophilia A and hemophilia B. In: Lichtman MA, et al, eds. Williams Hematology.7th ed. New York, NY: The McGraw-Hill Companies, Inc.; 2006:chap 115.

Review Date: 3/21/2008
Reviewed By: Stephen Grund, MD, PhD, Chief of Hematology/Oncology and Director of the George Bray Cancer Center at New Britain General Hospital, New Britain, CT. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.

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