Hemophilia B is a rare condition that causes you to bleed more than usual. It happens when you don't have enough of a special protein called factor IX that helps your blood clot. Usually, hemophilia B is inherited, or passed down through your family. The disease and its symptoms can be mild, moderate, or severe.
A mild case, in which you usually only bleed more if you get hurt or have surgery, is the most common type. If your hemophilia B is severe, you may often bleed for no reason. The bleeding may also be hidden inside your body.
There's no cure yet for hemophilia B, but treatments – and taking extra steps to avoid bleeding – can help you or your child live a normal life. We spoke to Madhurima Anne, MD, a hematologist oncologist at Hackensack Meridian Jersey Shore University Medical Center and Ocean University Medical Center in Brick, New Jersey, to learn more about this condition.
Q: Who gets hemophilia B and why?
A: Hemophilia B is an inherited bleeding disorder. It's rare compared to hemophilia A [the most common type of hemophilia], affecting about 1 in 15,000 to 1 in 30,000 male births worldwide. Because it's passed on by the X chromosome, men are mostly affected. Females tend to be carriers and are generally unaffected, although sometimes can also have milder bleeding symptoms.
Sometimes hemophilia B can be acquired through a new mutation. People also can develop an autoimmune "inhibitor," an antibody that can interfere with the function of factor IX.
Q: How and when is hemophilia B usually diagnosed?
A: Hemophilia B is usually diagnosed very early on, within the first 1 to 2 years of life. Per CDC data, the average age of diagnosis of severe hemophilia is around 1 month, moderate hemophilia is 8 months, and mild hemophilia, 36 months. The majority of patients with hemophilia will have a strong family history and will undergo screening. Some cases of mild hemophilia can be harder to diagnose, especially if they don't have a significant family history or aren't aware of their family history.
Suspected hemophilia means that you'll undergo basic screening for bleeding disorders, including a complete blood count (CBC), liver function, prothrombin time (PT) test, activated partial thromboplastin time (aPTT) test, and fibrinogen test. [These assess how well your blood can clot and measure how long it takes.]
A sample of your plasma may be mixed with normal plasma that has an adequate clotting factor. Correction of the aPTT [meaning that your blood returns to normal] suggests factor deficiency. This will prompt checking of factor levels VIII, IX, XI, and XII. If the mixing study does not correct, it suggests the presence of an inhibitor, and inhibitor testing will need to be sent.
A factor IX level lower than 40% suggests hemophilia B. Genetic testing is then performed to confirm.
Q: What are the most common symptoms?
A: Infants will generally have scalp bruises at birth. You may also find severe bleeding following early interventions such as heel sticks and circumcisions. Children will also have significant bruising or bleeding after minor injuries. Older children are at risk of joint bleeds, especially as they start to become more active or play sports.
The severity of the disease depends on the factor IX level, and is graded as mild, moderate, or severe. Mild is a factor IX level between 5% and 40%; moderate is a factor IX level between 1% and 5%; and severe is a factor IX level less than 1%.
In mild cases, bleeding usually occurs only after trauma or a surgical procedure and may not be diagnosed until you're an adult. In moderate cases, bruising and bleeding can occur after minor injuries, and is usually diagnosed in childhood.
Severe hemophilia puts you at risk of spontaneous bleeding, such as into muscles or joints in the absence of injury. One of the most feared complications is bleeding into the brain, either spontaneously or after a head trauma.
Q: How can these symptoms be treated and managed?
A: Many hemophilia B treatments, including standard or extended half-life factor IX replacement therapy and non-factor therapies (like marstacimab or f9-specific therapies), focus on preventing bleeds. Supportive medications (like aminocaproic acid and tranexamic acid) instead treat bleeding episodes when they happen.
If you have severe hemophilia B, a regular IV infusion of recombinant factor IX products can maintain safe factor IX levels before a first episode of significant bleeding. This may be started around age 1. After a bleeding episode, it can also help prevent future episodes and complications of recurrent bleeds. One of the complications of these types of infusions is that you can start to develop antibodies which counteract the benefit. Non-factor therapies also can control bleeding by activating other factors to allow clotting without replacing factor IX.
Recently, a one-time gene therapy was approved [for adults with] hemophilia B. In this case, your "defective" gene is replaced, which can increase the production of factor IX levels.
Q: What are the most common challenges of living with hemophilia B?
A: If you're affected as a child, you can have emotional stress from feared complications as well as activity restrictions. You may also be physically, emotionally, or financially burdened by medical treatment, such as repeated IVs and going into the hospital because of complications.
Hemophilia arthropathy can develop after recurrent joint bleeds. This can include arthritis, muscle weakness, nerve damage, reduced bone density with increased fracture risk, and bone damage that could require joint replacements.
If you have mild hemophilia, you'll also need to be vigilant about your bleeding tendencies. Before any surgery, which can place you at risk of prolonged post-op bleeding, notify your hematologist so that you receive the right management before, during, and after your procedure.
Be educated and aware of the risks and potential long-term complications in order to avoid them.
Q: What myths about hemophilia B need to be debunked?
A: There are a lot of myths and misconceptions out there when it comes to hemophilia B. Here are my top four:
- "It only affects boys." While hemophilia B is X-linked and mainly affects males, females can be carriers and may experience bleeding symptoms.
- "All cuts are life threatening." This isn't true. There are different degrees of bleeding.
- "Kids with hemophilia can't participate in sports." Depending on their factor levels, kids can generally participate in sports. Strategies such as routine factor replacement can be used if needed.
- "There is no treatment." There are several options, including factor replacement as well as newer options such as gene therapy.
Q: What's the outlook for people who live with hemophilia B?
A: The prognosis of hemophilia B has improved dramatically, with normal or near-normal life expectancy.Access to preventive therapy is crucial for preventing complications in early infancy.