Hemophilia B (patient information)
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What is Hemophilia B?
Hemophilia B is a hereditary bleeding disorder caused by a lack of blood clotting factor IX. Without enough factor IX, the blood cannot clot properly to control bleeding.
What are the symptoms of Hemophilia B?
The severity of symptoms can vary, and the severe forms become apparent early on.
Bleeding is the main symptom of the disease and sometimes, although 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.
Symptoms can 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
What causes Hemophilia B?
Hemophilia B 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 gene on the other chromosome can do the job of making enough factor IX.
Males, however, have only one X chromosome, so if the factor IX gene on that chromosome is defective, they will have Hemophilia B. Therefore, 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 a woman who carries the defective gene have a 50% chance of having hemophilia B, while 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
Who is at risk for Hemophilia B?
How do I know I have Hemophilia B?
If the patient is the first person in the family to have a suspected bleeding disorder, he or she 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.
Tests results may include:
- Prolonged partial thromboplastin time (PTT)
- Normal prothrombin time
- Normal bleeding time
- Normal fibrinogen level
- Low factor IX
When to seek urgent medical care
Treatment options
Where to find medical care for Hemophilia B
Directions to Hospitals Treating Hemophilia B