What Is Hemophilia B?

Written by Marijke Vroomen Durning, RN
Medically Reviewed by Neha Pathak, MD on January 07, 2026

Hemophilia B is a rare genetic disorder that makes it hard for your blood to clot. If you have a cut, scrape, or other injury, you will bleed for longer than people who don’t have a bleeding disorder. The typical image of someone with hemophilia is that they cut themselves and have a hard time stopping the blood. But bleeding can also occur internally, inside your body, like in your muscles and joints. Bleeding can happen spontaneously, meaning that there’s no cut or bump that might have caused it.

There are two main types of hemophilia: A (the most common) and B. The B type is sometimes called Christmas disease.

Hemophilia B can be divided into three types:

Severe. If you have severe hemophilia B, you likely were diagnosed early in life, probably before your second birthday. People with severe hemophilia B have between two and five spontaneous bleeds each month. You can bleed into your joints, and if you hurt yourself, you will bleed longer than is typical. You could also experience more swelling, pain, and bleeding from usually minor procedures, like having a tooth pulled.

Moderate. You may be diagnosed with moderate hemophilia B as old as 5 or 6 years. If you have moderate disease, you still have prolonged bleeding but not as often as with severe hemophilia B, so it might not be as obvious as the severe type. Spontaneous bleeding might happen as often as once a month or as infrequently as once a year.

Mild. Mild hemophilia B might not be diagnosed for a long time. If you have it, you won’t have spontaneous bleeding. However, you’ll have a few episodes of abnormal bleeding after you’ve had surgery or a tooth pulled. It could happen anywhere from once a year to once every 10 years.

There is an even rarer form of hemophilia called hemophilia C. It’s also called factor XI deficiency, plasma thromboplastin antecedent (PTA) deficiency, or Rosenthal syndrome.

You need different proteins for your blood to clot. One is called factor IX. Hemophilia B is caused by having not enough factor IX or having damaged factor IX. The disease is mostly passed down through families, usually through the mother on the X chromosome. (Chromosomes determine your sex. Females are generally XX chromosomes and males XY.) Rarely, hemophilia B can happen spontaneously — or out of the blue — even if you don’t have any family history. 

Scientists don’t know what causes the damage to the gene or why some people are missing it.

The main symptoms for hemophilia B are bleeding for longer than normal, bleeding into joints and potentially damaging them, and bruising easily.

If you have bleeding in a muscle or joint, this can hurt, especially when you move. Usually the muscle or joint becomes swollen and inflamed. With this disease, even a small bump to your head can lead to serious consequences. 

When hemophilia B is diagnosed depends on many factors, including how severe it is. In the first six months of life, since babies usually don't fall or get hurt often, an early diagnosis is rare. If it’s your child who has the disease, and it’s severe or moderate, you may notice issues once your baby becomes more active. As babies begin to crawl, they may get bumps and raised bruises. There may be bleeding in the joints. Bruising and long-lasting bleeding from even small injuries may cause a doctor to suspect hemophilia.

The doctor may ask:

  • What happened to cause your child's bumps, bruises, or bleeding?
  • How long did the bleeding last?
  • Are they taking any medication?
  • Do they have any other medical conditions or concerns?

Your doctor will also ask about your family's medical history to find out if anyone had a problem with bleeding or blood clotting.

To get the diagnosis, doctors will run blood tests to find out how long it takes to clot. They’ll check for any missing clotting factors.

 

You could be diagnosed with mild hemophilia B as an adult. If you’ve noticed that you tend to bleed longer than seems normal or you bleed very easily, your doctor will want to know more about your history. They’ll order tests to see if you have the disease or if your symptoms are explained by another condition.

If you or a loved one is diagnosed with hemophilia B, you'll probably have a lot of questions. You might want to ask your doctor:

  • Is this a severe case?
  • Have you treated someone with this condition before?
  • What treatment do you recommend?
  • How often will we need to come to the doctor's office?
  • How long is too long to bleed from a small cut?
  • What do we need to look out for? Are some symptoms more serious than others?
  • Are there over-the-counter medicines we should or shouldn't use?
  • How do we keep safe? Do we need to limit activities?
  • Do we need to make teachers and care providers aware?
  • How do we connect with other families who have kids with hemophilia?
  • What are the chances others in our family will have hemophilia? 

Finding expert care for hemophilia B is important, but it can depend a lot on where you live and what resources are available near you. Hemophilia treatment centers (HTCs) are the best place to start. The CDC hosts an HTC directory where you can look for centers close to you. 

The staff at the centers focus on coordinated care, helping with not just the medical treatment needed to treat hemophilia B, but also the mental health aspects and how to live with it day by day. Your care team could include different experts or professionals: 

The National Bleeding Disorders Foundation has a Resources Near You section, which is another good place to look for assistance and expert hemophilia care.

There is no cure for hemophilia B, but you or your child can manage the condition and enjoy an active life. With standard replacement therapy, you’ll get the factor IX your body doesn't make.  When hemophilia B is severe, you or your child may need regular treatments to prevent bleeding. Otherwise, you’ll need to rely on treatment to stop bleeding after it starts. 

You can get replacement therapy at a clinic or from a visiting nurse. In many cases, you can learn to do it at home. There are newer treatment options and classes of medications you may wish to consider and talk with your doctor about, too. Medications to treat hemophilia B include:

Plasma-derived factor IX concentrates. Before 1992, all treatments to replace the clotting factor that’s missing in hemophilia B came from healthy human plasma. Plasma is the liquid part of your blood. These medicines aren’t used as often today now that newer treatment options are available.

Plasma-derived factor IX treatments for hemophilia B include:

  • AlphaNine SD
  • Profilnine SD

Recombinant factor IX concentrates. Instead of coming from human plasma, recombinant medicines are made in a lab. Because they don’t contain human plasma, they come with less risk for viruses. But it’s possible your body could start making inhibitors that work against the medicines. Some recombinant factor medicines are known as extended half-life (EHL) medicines. That’s because they’re modified in ways that make them last longer.

Standard half-life recombinant factor IX therapies approved for hemophilia B include:

  • Nonacog alfa (Benefix)
  • Trenonacog alfa (Ixinity)
  • Nonacog gamma (Rixubis)

Extended half-life (EHL) recombinant therapies for hemophilia B include:

  • Eftrenonacog alfa (Alprolix)
  • Albutrepenonacog alfa (Idelvion)
  • Nonacog beta pegol (Rebinyn)

Gene therapy. In gene therapy, you’ll receive a virus (not the kind that makes you sick) that’s been modified to carry the clotting gene you’re missing. The virus delivers the gene to cells in your liver so that you can start to make your own clotting factor IX. Gene therapy may be an option if you’re an adult with factor IX levels of 2% or lower. The FDA approved the first gene therapy for hemophilia B in 2022. It’s called Hemgenix (etranacogene dezaparvovec).

Rebalancing, bypassing, or non-factor therapies. Medicines in this group work in different ways to help your blood clot and protect you from bleeding episodes. For example, they may block other proteins that slow clotting or fill in for factor IX without replacing it. Other treatments approved in the U.S. for hemophilia B include:

  • Concizumab (Alhemo)
  • Fitusiran (Qfitlia)
  • Marstacimab (Hympavzi)

The FDA expanded the approval of marstacimab (Hympavzi) to include adults and children ages 6 and older with hemophilia A or B, with or without inhibitors.

Aside from the obvious bleeding, hemophilia B can cause other complications, such as:

  • Muscle damage from internal bleeding
  • Nerve damage from muscle swelling pressing on the nerves
  • Joint damage from bleeding into the joint space
  • Reactions to the treatments, such as allergic reactions or infections

Whether it’s you or your child who has hemophilia B, there are some things you should prepare for so you’re ready before any bleeding episodes. Quick first aid is important. Clean any small cuts, scrapes, and injuries, and apply pressure and a bandage right away. Serious injuries need medical attention.

Exercise and keeping a healthy weight are important, too. Working out helps strengthen muscles, which can reduce bleeding from injuries. Extra weight puts more strain on the body, and that can increase problems from bleeding. Avoid high-risk activities that may lead to head injuries. 

Make sure all your health care providers are aware of you or your loved one’s condition. They may need to take medications to help clot their blood before certain procedures, like dental work.

Try to avoid injuries. Make sure your child wears knee pads, elbow pads, and a helmet while playing. Use safety straps in car seats, strollers, and high chairs. Check your home and yard for possible problems like sharp edges.

What to expect

With the right precautions and planning, you or your child can expect to keep doing all the things you love to do while being prepared for emergencies. Have your doctor’s contact information available to everyone who cares for your child and anyone you spend time with regularly. Be sure to follow any treatment plans and see the doctor regularly. By taking care of yourself, you can expect to live a healthy and active life with hemophilia B.

There are a few hemophilia B organizations that you can reach out to for support. Some good ones to start with include:

Living with a chronic disease can be stressful, especially one that can cause such serious complications. It’s important to take care of your emotional and mental health in addition to your physical health. Reaching out to the hemophilia organizations can help you feel less alone. There are group chapters all over the country, as well as online options. 

If you’re struggling with your mental health, reach out to friends and family. Ask your care team for help. Ask if your hemophilia care team includes mental health professionals, too. They will be specially trained and experienced in working with people living with this disease. If not, ask your doctor to refer you to a mental health professional experienced with chronic disease.

Caring for a child with hemophilia B can mean that you put all your efforts into them. You might forget about your own needs in the meantime. It’s important that you as a caregiver don’t forget to take time to care for yourself. Being strong and handling things on your own without asking for help can lead to burnout. You might get sick as well.

The hemophilia organizations also help caregivers, so you can search for local chapters or, if you prefer, online contacts. And don’t forget about your child’s hemophilia care team. They will likely have resources or recommendations for you as well.

Hemophilia B is a lifelong disease that can lead to complications like joint and muscle damage. Because severe or moderate hemophilia B can lead to life-threatening bleeding, it can be stressful living with the disease. Treatments can help the blood to clot, but it’s important to learn the signs of internal bleeding and when to go for help. You can live a long and active life with hemophilia B as long as you follow your treatment plan and take precautions to prevent injury as much as possible.

What is the life expectancy of someone with hemophilia B?

With proper treatment, the life expectancy of someone with hemophilia B is close to that of someone without the disease.

Why is hemophilia B called the Christmas disease?

Hemophilia B is sometimes called Christmas disease because the first patient to be identified as having it was named Stephen Christmas. He had the signs of having hemophilia but wasn’t missing factor VIII, which – at the time – doctors knew caused hemophilia. Researchers found that Stephen was missing a different clotting factor, so they called it Christmas disease. Only later did scientists divide the two main types of hemophilia into A and B.

What's the difference between hemophilia A and hemophilia B?

Hemophilia A is caused by missing or damaged clotting factor VIII, which is needed for blood to clot normally. If you lack clotting factor IX instead, you have the B type.

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