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Hemophilia B

What is Hemophilia B?

Hemophilia B (or Christmas disease) is less common than hemophilia A and results when the person does not have enough clotting factor IX. Although hemophilia B is usually inherited, about one third of cases are caused by a spontaneous mutation in the person’s own genes. 

Hemophilia B affects about 1 in 20,000 people and is diagnosed by taking a blood sample and measuring the level of factor activity in the blood. 

Hemophilia B can be mild, moderate, or severe, depending on how much clotting factor is in an affected person's blood. However, approximately two thirds of patients have moderate to severe hemophilia B. People with hemophilia B have prolonged bleeding after an injury, surgery, or tooth extraction. In severe cases, they may bleed once or twice a week and often the bleeding is spontaneous, which means it happens for no obvious reason. Serious complications can result from bleeding into the joints, muscles, brain, or other internal organs. See how bleeds, infusions and Factor IX levels may be affecting you more than you think. In mild cases of hemophilia B, the disorder may remain unknown until after a surgery or serious injury.

Treatment for hemophilia B is very effective and with appropriate treatment and care, people with hemophilia B can live perfectly normal lives. The main treatment is called replacement therapy, during which clotting factor IX is infused into a vein either prophylactically (preventatively) or on-demand to prevent or treat bleeds.

Hemophilia B patient Michael Joshua

Living (and Thriving) with Hemophilia B

"Don't be scared to live your life. Don't let hemophilia hold you back." These inspiring words came from college-bound hemophilia B patient Michael Joshua.

Watch his story

Resources for you

Resource Description  
B in the Know Explains the impact bleeds can have on the life of a hemophilia B patient. View Website 
IDELVION Facebook Page Provides hemophilia B patients and their families with information on IDELVION, patient stories and support programs. Go to Facebook
World Federation of Hemophilia A global organization aiming to improve and sustain care for people with inherited bleeding disorders. View Website
National Hemophilia Foundation A U.S. organization dedicated to finding better treatments and cures for inheritable bleeding disorders. View Website
Hemophilia Federation of America A U.S. nonprofit organization that assists and advocates for the bleeding disorders community. View Website
Product Websites (United States) (United States)


Treatments Available

Availability of treatments may vary from country to country. Please be sure to visit your local site for further information.

IDELVION® | Coagulation Factor IX (Recombinant), Albumin Fusion Protein

US Prescribing Information

US Important Safety Information(Selected) 

Stop treatment and immediately contact your healthcare provider if you see signs of an allergic reaction, including a rash or hives, itching, tightness of chest or throat, difficulty breathing, lightheadedness, dizziness, nausea, or a decrease in blood pressure.


In clinical trials for IDELVION, headache was the only side effect occurring in more than 1% of patients (1.8%), but is not the only side effect possible. Tell your healthcare provider about any side effect that bothers you or does not go away, or if bleeding is not controlled with IDELVION.

Full US Important Safety Information

HEMGENIX® | (etranacogene dezaparvovec-drlb) suspension, for intraveneous infusion

US Prescribing Information

US Important Safety Information(Selected) 

In clinical trials for HEMGENIX, the most common side effects reported in more than 5% of patients were liver enzyme elevations, headache, elevated levels of a certain blood enzyme, flu-like symptoms, infusion-related reactions, fatigue, nausea, and feeling unwell. These are not the only side effects possible. Tell your healthcare provider about any side effect you may experience.

Full US Important Safety Information

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