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Hemophilia B

Haemophilia B, Christmas disease, Hemophilia, familial, Hemophilia, hereditary

Overview

Hemophilia is a bleeding disorder that slows the blood clotting process. People with this condition experience prolonged bleeding or oozing following an injury, surgery, or having a tooth pulled. In severe cases of hemophilia, continuous bleeding occurs after minor trauma or even in the absence of injury (spontaneous bleeding). Serious complications can result from bleeding into the joints, muscles, brain, or other internal organs. Milder forms of hemophilia do not necessarily involve spontaneous bleeding, and the condition may not become apparent until abnormal bleeding occurs following surgery or a serious injury.

The major types of this condition are hemophilia A (also known as classic hemophilia or factor VIII deficiency) and hemophilia B (also known as Christmas disease or factor IX deficiency). Although the two types have very similar signs and symptoms, they are caused by mutations in different genes. People with an unusual form of hemophilia B, known ashemophilia B Leyden, experience episodes of excessive bleeding in childhood but have few bleeding problems after puberty.

Symptoms - Hemophilia B

Symptoms may 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

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 boy 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 or in response to surgery. Internal bleeding may occur anywhere. 

Causes - Hemophilia B

Changes in the F9 gene are responsible for hemophilia B (while mutations in the F8 gene cause hemophilia A). The F9 gene provides instructions for making a protein called coagulation factor IX. Coagulation factors are proteins that work in the blood clotting process. After an injury, blood clots protect the body by sealing off damaged blood vessels and preventing excessive blood loss.

Mutations in the F9 gene lead to the production of an abnormal version of coagulation factor IX, or reduce the amount of one of these proteins. The altered or missing protein cannot participate effectively in the blood clotting process. As a result, blood clots cannot form properly in response to injury. These problems with blood clotting lead to continuous bleeding that can be difficult to control. The mutations that cause severe hemophilia almost completely eliminate the activity of coagulation factor IX. The mutations responsible for mild and moderate hemophilia reduce but do not eliminate the activity of one of these proteins.

Another form of the disorder, known as acquired hemophilia, is not caused by inherited gene mutations. This rare condition is characterized by abnormal bleeding into the skin, muscles, or other soft tissues, usually beginning in adulthood.  The production of autoantibodies is sometimes associated with pregnancy, immune system disorders, cancer, or allergic reactions to certain drugs. In about half of cases, the cause of acquired hemophilia is unknown.

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

Prevention - Hemophilia B

Genetic counseling is 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.

For a female carrier, there are four possible outcomes for each pregnancy:

  1. A girl who is not a carrier
  2. A girl who is a carrier
  3. A boy without hemophilia
  4. A boy with hemophilia

Diagnosis - Hemophilia B

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:

  • Low factor IX
  • Partial thromboplastin time (PTT)
  • Normal Prothrombin time
  • Normal bleeding time
  • Normal Fibrinogen level

Prognosis - Hemophilia B

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 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.

Treatment - Hemophilia B

The main medication to treat hemophilia B is concentrated FIX product, called clotting factor or simply factor. Recombinant factor products, which are developed in a lab through the use of DNA technology, ,preclude the use of human-derived pools of donor-sourced plasma. And while plasma-derived FIX  products are still available, approximately 75% of the hemophilia community takes a recombinant FIX product.

These factor therapies are infused intravenously through a vein in the arm or a port in the chest. The Medical and Scientific Advisory Council (MASAC) of the National Hemophilia Foundation encourages the use of recombinant clotting factor products because they are safer. Your doctor or your HTC will help you decide which is right for you.

Patients with severe hemophilia may be on a routine treatment regimen, called prophylaxis, to maintain enough clotting factor in their bloodstream to prevent bleeds. Prophylaxis is recommended as optimal therapy for children with severe hemophilia B.

Aminocaproic acid is an antifibrinolytic, preventing the breakdown of blood clots. It is often recommended before dental procedures, and to treat nose and mouth bleeds. It is taken orally, as a tablet or liquid. It's recommended a dose of clotting factor be taken first to form a clot, then aminocaproic acid, to preserve the clot and keep it from being broken down prematurely

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

Resources - Hemophilia B

 

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