What is Hemophilia type B?
Hemophilia B is a genetic disorder caused by missing or defective Factor IX clotting protein.
It also is inherited, and like hemophilia A, it can be caused by a spontaneous genetic mutation in one-third of cases. This type of hemophilia also affects all ethnic groups equally, but it is about four times rarer than hemophilia A.
Hemophilia B can cause prolonged bleeding or oozing after an injury or surgery, and in severe cases bleeding may occur even in the absence of injury.
People with an unusual form of hemophilia B, known as hemophilia B Leyden, experience episodes of excessive bleeding in childhood, but report few problems after puberty.
Genetics of Hemophilia type B
Hemophilia B also is carried in the X chromosome, in an X-linked recessive manner, meaning that two hemophilia-carrying X chromosomes must be inherited for the disease to be active in women, but only in one X chromosome in men.
Females inherit two XX chromosomes, one from their mother and one from their father (XX). Males inherit an X chromosome and a Y chromosome from their father (XY). This means that if a son inherits an X chromosome from his mother that carries hemophilia, he will have hemophilia. But because women receive two X chromosomes, they develop the disease only only if the two carry the defective gene.
Symptoms of hemophilia type B
Symptoms of hemophilia B include X-linked recessive inheritance, reduced factor IX activity, prolonged whole-blood clotting time, prolonged partial thromboplastin time, persistent bleeding after trauma, osteoarthritis, joint hemorrhage, gastrointestinal hemorrhage and generalized abnormal bleeding.
Hemophilia B should be diagnosed at a specialized medical facility. Genetic tests that assess a patient’s clotting time and the ability to form a clot may be ordered to confirm the diagnosis.
To know more about genetics of hemophilia B, you may visit these resources:
- GeneReviews – A National Center for Biotechnology Information webpage with updated, expert-authored, peer-reviewed, full-text articles describing the process of genetic testing from diagnosis to management.
- The National Hemophilia Foundation – A website with guidelines for management of pregnancy and delivery of women with bleeding disorders and carriers of hemophilia A and B.
Stages of hemophilia type B
There are three stages of hemophilia B: mild, moderate and severe. Mild hemophilia is when there is between 6% and 49% clotting factor protein in the blood. Moderate hemophilia is when there is between 1% and 5% clotting factor protein in the blood. Severe hemophilia is when there is less than 1% clotting factor protein in the blood.
Treatment of hemophilia type B
Treatment of hemophilia B is a lifelong management approach that should be monitored by a specialized team. There are a series of orphan products approved by the U.S. Food and Drug Administration (FDA) for hemophilia B, including:
- AlphaNine (coagulation factor IX [human]) – AlphaNine is approved for use as replacement therapy for the prevention and control of bleeding episodes and during surgery to correct defective hemostasis (manufactured by Alpha Therapeutic Corporation).
- Alprolix (coagulation factor IX [recombinant]) – Alprolix is approved for control and prevention of bleeding episodes, perioperative management, and routine prophylaxis to prevent or reduce the frequency of bleeding episodes in adults and children (manufactured by Biogen).
- BeneFix (coagulation factor IX [recombinant]) – BeneFix is approved for the control and prevention of hemorrhagic episodes, including control and prevention of bleeding in surgical settings (manufactured by Wyeth Pharmaceuticals).
- Mononine (coagulation factor IX) – Mononine is approved for the prevention and control of bleeding in factor IX deficiency (manufactured by CSL Behring).
- NovoSeven (coagulation factor VIIa [recombinant]) – NovoSeven is approved for the treatment of bleeding episodes in people with factor VII deficiency and for the treatment of perioperative management of Glanzmann’s thrombasthenia with refractoriness to platelet transfusions (manufactured by Novo Nordisk).
- rIX-FP (recombinant fusion protein linking coagulation factor IX with albumin) – rIX-FP is approved for the control and prevention of bleeding episodes, for the perioperative management of bleeding, and for routine prophylactic treatment (manufactured by CSL Behring).
- Rixubis (coagulation factor IX [recombinant]) – Rixubis is approved for routine prophylactic treatment for the prevention or reduction of the frequency of bleeding episodes in adults (manufactured by Baxalta).
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