Hemophilia is a disorder in which a person’s blood does not clot normally, which can lead to spontaneous or excessive bleeding, according to the Centers for Disease Control and Prevention (CDC). (1)

Blood contains proteins called clotting factors, which can help to stop bleeding, the CDC notes. People with hemophilia have lower-than-normal levels of certain clotting factors, which can make bleeding more likely to occur.

Hemophilia is a genetic disorder that can manifest later in life — usually in middle-aged or older people, or women who have just given birth or are in the final months of pregnancy.

Hemophilia is rare and it mostly affects males, according to KidsHealth. (2) It can be mild, moderate, or severe, depending on how much clotting factor is in the blood.

Types of Hemophilia

Hemophilia A (Classic Hemophilia)

The most common type of hemophilia, hemophilia A, is caused by an insufficient amount of clotting factor 8.

It is an inherited disorder (passed down from parents to children), but about one-third of cases are caused by a spontaneous gene mutation, or a change in a gene, according to the National Hemophilia Foundation (NHF). (3)

Hemophilia A is much more common in males. It rarely occurs in females.

People with hemophilia A typically bleed for longer periods of time than other people. Two types of bleeding can occur: internal bleeds, which occur in joints and muscles, and external bleeds, from minor cuts, dental procedures, or trauma.

Hemophilia B (Christmas Disease)

Hemophilia B results from insufficient amounts of clotting factor 9. (1)

Like hemophilia A, it’s a genetic disorder, with about one-third of cases caused by a spontaneous mutation, per the NHF. (4) People with hemophilia B bleed for longer periods of time than people who don't have the disorder. Bleeding can occur internally, in joints and muscles, or externally, from minor cuts, dental procedures, or trauma. Hemophilia B is rare in women.

People with an unusual form of hemophilia B, known as hemophilia B Leyden, have undetectable levels of factor 9 early in life but increasing levels over time, according to the National Organization of Rare Diseases (NORD). (5) By middle age, they may no longer need treatment for bleeding episodes.

Hemophilia C (Factor 11 Deficiency)

Hemophilia C is caused by a lack of clotting factor 11, per NORD. (6) Unlike types A and B, spontaneous bleeding or bleeding into joints does not occur unless there is underlying joint disease. A more likely scenario for a person with hemophilia C is extended bleeding after surgery, dental procedures, or trauma. Men and women are equally affected by hemophilia C.

Acquired Hemophilia

While hemophilia is usually an inherited disorder, a rare autoimmune disorder called acquired hemophilia can develop later in life, notes NORD. (7) It happens when your immune system attacks clotting factors in the blood, according to the Mayo Clinic. (8) Scientists believe this can happen as a result of an infection or underlying disorder, and sometimes for no identifiable reason. (7) Acquired hemophilia can occur at any age but is most common among elderly people. It can also be associated with pregnancy, autoimmune conditions, cancer, and multiple sclerosis. (8)

Signs and Symptoms of Hemophilia

Common signs and symptoms of hemophilia include: (1)

  • Bleeding into the joints, which can cause swelling and pain or tightness in the joints (often the knees, elbows, and ankles)
  • Bleeding into the skin (bruising) or into muscle and soft tissue, causing an accumulation of blood (hematoma)
  • Bleeding of the mouth and gums, and bleeding that is difficult to stop after losing a tooth
  • Bleeding after circumcision
  • Bleeding after having shots or vaccines
  • Bleeding in the head of an infant after the baby is delivered
  • Blood in the urine or stool
  • Frequent bleeding and nosebleeds that are difficult to stop.

Learn More About Signs and Symptoms of Hemophilia

Causes and Risk Factors of Hemophilia

In most cases, hemophilia is a genetic, or inherited, disease.

In hemophilia A and B, the gene for hemophilia is carried on the X chromosome. (3,4) Females inherit two X chromosomes; one from their mother and one from their father. Males inherit an X chromosome from their mother and a Y chromosome from their father. If a son inherits an X chromosome carrying hemophilia from his mother, he will have hemophilia. Fathers can’t pass hemophilia on to their sons (because boys inherit a Y chromosome from their fathers, and hemophilia is X-linked).

Even if females inherit the hemophilia gene from their mother, they are likely to inherit a healthy X chromosome from their father, so they are unlikely to have hemophilia. A daughter who inherits an X chromosome that has a mutation in the gene for hemophilia is called a carrier, and she can pass the gene on to her children. Hemophilia rarely occurs in daughters.

About 30 percent of people with hemophilia have no history of the disorder in their family, but it manifests when an unexpected change occurs in one of the genes associated with hemophilia. (8)

How Hemophilia C Is Inherited

A deficiency in clotting factor 11 is caused by mutations to the F11 gene. (6) It is usually inherited, but in rare instances, new or spontaneous mutations may occur in an individual, causing the disorder.

Duration of Hemophilia

There is currently no cure for hemophilia, according to the NHF. (13)

Complications of Hemophilia

One of the most serious (but rare) complications of hemophilia is a head injury that causes bleeding in the brain. (8) Symptoms include double vision; painful, long-lasting headache; repeated vomiting; sleepiness; seizures or convulsions; and sudden weakness or clumsiness.

Another serious, but chronic, complication with hemophilia is the development of inhibitors, which make it more difficult to stop a bleeding episode and can increase your risk of death. About 1 in 5 people with hemophilia A develop inhibitors, though scientists still do not fully understand who will get them and why, notes the CDC. (19) In hemophilia B, the development of inhibitors is much less common, according to a study published in September 2018 in Seminars in Thrombosis and Hemostasis. (20) In hemophilia C, inhibitors can develop, but it’s unclear how often it happens. (6)

It’s important that people with hemophilia who use clotting factor concentrates get a blood test for inhibitors at least once a year. (19) If you’re eligible, you can receive free inhibitor testing at federally funded hemophilia treatment centers provide through the Community Counts Registry for Bleeding Disorders Surveillance program.

Learn More About the Complications of Hemophilia: How It Affects Your Body in the Short and Long Term

Related Conditions and Their Causes

Von Willebrand disease

Von Willebrand disease (VWD), the most common bleeding disorder, is an inherited disorder caused by missing or defective von Willebrand factor (VWF), a blood clotting protein, according to the NHF. (23)

VWD affects up to 1 percent of the U.S. population. It is carried on chromosome 12 and occurs in males and females at the same rate.

Resources We Love

Centers for Disease Control and Prevention (CDC)

The CDC’s page on hemophilia has links to articles, videos, patient stories, and the Community Counts project to gather data about Americans living with bleeding disorders.

Mayo Clinic

Mayo Clinic is a trusted resource for health and medical information, including information about hemophilia.

National Hemophilia Foundation (NHF)

The NHF is dedicated to finding better treatments and a cure for inheritable bleeding disorders. It does this through awarding research grants and through political advocacy at all levels of government. It also offers opportunities for community education and support through its local chapters, and has a camp locator for children with bleeding disorders.

World Federation of Hemophilia (WFH)

Located in Montreal and working globally, the WFH’s mission is “to close the gap in care between those who receive proper treatment and those who do not.” It works toward this goal by supporting programs around the world to improve medical care for those with bleeding disorders and make treatment products more accessible.

Editorial Sources and Fact-Checking

  1. What Is Hemophilia? Centers for Disease Control and Prevention. July 17, 2020.
  2. Hemophilia. KidsHealth. February 2020.
  3. Hemophilia A. National Hemophilia Foundation.
  4. Hemophilia B. National Hemophilia Foundation.
  5. Hemophilia B. National Organization for Rare Disorders. 2018.
  6. Factor XI Deficiency. National Organization for Rare Disorders. 2020.
  7. Acquired Hemophilia. National Organization for Rare Diseases. 2016.
  8. Hemophilia. Mayo Clinic. August 7, 2020.
  9. Diagnosis of Hemophilia. Centers for Disease Control and Prevention. July 17, 2020.
  10. Hemophilia: Outlook/Prognosis. Cleveland Clinic. January 17, 2020.
  11. Introduction to Hemophilia. World Federation of Hemophilia. May 2012.
  12. Hemophilia. Cleveland Clinic. January 17, 2020.
  13. Fast Facts. National Hemophilia Foundation.
  14. Hemophilia Treatment Centers. Centers for Disease Control and Prevention. July 17, 2020.
  15. Treatment of Hemophilia. Centers for Disease Control and Prevention. July 17, 2020.
  16. Perrin GQ, Herzog RW, Markusic DM. Update on Clinical Gene Therapy for Hemophilia. Blood. January 31, 2019.
  17. BioMarin Receives Complete Response Letter (CRL) from FDA for Valoctocogene Roxaparvovec Gene Therapy for Severe Hemophilia A. BioMarin.com. August 19, 2020.
  18. Paredes AC, Costa P, Fernandes S, et al. Effectiveness of Hypnosis for Pain Management and Promotion of Health-Related Quality-of-Life Among People With Haemophilia: A Randomised Controlled Pilot Trial. Scientific Reports. September 2019.
  19. Inhibitors and Hemophilia. Centers for Disease Control and Prevention. July 17, 2020.
  20. Santoro C, Quintavalle G, Castaman G, et al. Inhibitors in Hemophilia B. Seminars in Thrombosis and Hemostasis. September 2018.
  21. Data & Statistics on Hemophilia. Centers for Disease Control and Prevention. July 17, 2020.
  22. Hemophilia A. StatPearls. July 20, 2020.
  23. Von Willebrand Disease. National Hemophilia Foundation.
  24. McLaughlin J, Lambing A, Witkop ML, et al. Racial Differences in Chronic Pain and Quality of Life among Adolescents and Young Adults with Moderate or Severe Hemophilia. Journal of Racial and Ethnic Health Disparities. 2016.
  25. New Online Space for Black/African Americans with Bleeding Disorders. National Hemophilia Foundation. August 8, 2020.


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