of Genetic Terms
Definitions for the genetic terms used on this page
Learning About Hemophilia
What is hemophilia?
Hemophilia is a bleeding disorder that slows down the blood clotting process. People who have hemophilia often have longer bleeding after an injury or surgery. People who have severe hemophilia have spontaneous bleeding into the joints and muscles. Hemophilia occurs more commonly in males than in females.
The two most common types of hemophilia are hemophilia A (also known as classic hemophilia) and hemophilia B (also known as Christmas disease). People who have hemophilia A have low levels of a blood clotting factor called factor eight (FVIII). People who have hemophilia B have low levels of factor nine (FIX).
The two types of hemophilia are caused by permanent gene changes (mutations) in different genes. Mutations in the FVIII gene cause hemophilia A. Mutations in the FIX gene cause hemophilia B. Proteins made by these genes have an important role in the blood clotting process. Mutations in either gene keep clots from forming when there is an injury, causing too much bleeding that can be difficult to stop.
Hemophilia A is the most common type of this condition. One in 5,000 to 10,000 males worldwide have hemophilia A. Hemophilia B is less common, and it affects 1 in 20,000 to 34,500 males worldwide.
What are the symptoms of hemophilia?
Symptoms of hemophilia include prolonged oozing after injuries, tooth extractions or surgery; renewed bleeding after initial bleeding has stopped; easy or spontaneous bruising; and prolonged bleeding.
In both severe hemophilia A and severe hemophilia B, the most frequent symptom is spontaneous joint bleeding. Other serious sites of bleeding include the bowel, the brain and soft tissues. These types of bleeding can lead to throwing up blood or passing blood in the stool, stroke, and sudden severe pain in the joints or limbs. Painful bleeding into the soft tissues of the arms and legs can lead to nerve damage.
Individuals who have severe hemophilia are usually diagnosed within the first year of life. People who have moderate hemophilia do not usually have spontaneous bleeding, but they do have longer bleeding and oozing after small injuries. They are usually diagnosed before they reach five or six years.
Individuals who have mild hemophilia do not have spontaneous bleeding. If they are not treated they may have longer bleeding when they have surgery, teeth removed or major injuries. Individuals with mild hemophilia may not be diagnosed until later in life.
How is hemophilia diagnosed?
Hemophilia A and B are diagnosed by measuring factor clotting activity. Individuals who have hemophilia A have low factor VIII clotting activity. Individuals who have hemophilia B have low factor IX clotting activity.
Genetic testing is also available for the factor VIII gene and the factor IX gene. Genetic testing of the FVIII gene finds a disease-causing mutation in up to 98 percent of individuals who have hemophilia A. Genetic testing of the FIX gene finds disease-causing mutations in more than 99 percent of individuals who have hemophilia B.
Genetic testing is usually used to identify women who are carriers of a FVIII or FIX gene mutation, and to diagnose hemophilia in a fetus during a pregnancy (prenatal diagnosis). It is sometimes used to diagnose individuals who have mild symptoms of hemophilia A or B.
What is the treatment for hemophilia?
There is currently no cure for hemophilia. Treatment depends on the severity of hemophilia.
Treatment may involve slow injection of a medicine called desmopressin (DDAVP) by the doctor into one of the veins. DDAVP helps to release more clotting factor to stop the bleeding. Sometimes, DDAVP is given as a medication that can be breathed in through the nose (nasal spray).
People who have moderate to severe hemophilia A or B may need to have an infusion of clotting factor taken from donated human blood or from genetically engineered products called recombinant clotting factors to stop the bleeding. If the potential for bleeding is serious, a doctor may give infusions of clotting factor to avoid bleeding (preventive infusions) before the bleeding begins. Repeated infusions may be necessary if the internal bleeding is serious.
When bleeding has damaged joints, physical therapy is used to help them function better. Physical therapy helps to keep the joints moving and prevents the joints from becoming frozen or badly deformed. Sometimes the bleeding into joints damages them or destroys them. In this situation, the individual may be given an artificial joint.
When a person who has hemophilia has a small cut or scrape, using pressure and a bandage will take care of the wound. An ice pack can be used when there are small areas of bleeding under the skin.
Researchers have been working to develop a gene replacement treatment (gene therapy) for Hemophilia A. Research of gene therapy for hemophilia A is now taking place. The results are encouraging. Researchers continue to evaluate the long-term safety of gene therapies. The hope is that there will be a genetic cure for hemophilia in the future.
Individuals who have hemophilia A and B are living much longer and with less disability than they did 30 years ago. This is because of the use of the intravenous infusion of factor VIII concentrate, home infusion programs, prophylactic treatment, and improved patient education.
Is hemophilia inherited?
Hemophilia is inherited in an X-linked recessive pattern. A condition is considered X-linked when gene mutation that causes it is located on the X chromosome, one of the two sex chromosomes. In males (who have only one X chromosome), one altered copy of the gene in each cell is enough to cause the condition. Since females have two X chromosomes, a mutation must be present in both copies of the gene to cause the hemophilia. Males are affected by X-linked recessive disorders much more frequently than females. A major characteristic of X-linked inheritance is that fathers cannot pass X-linked traits to their sons.
A female who is a carrier has a 1 in 2 (50 percent) chance to pass on her X chromosome with the gene mutation for hemophilia A or B to a boy who will be affected. She has a 1 in 2 (50 percent) chance to pass on her X chromosome with the normally functioning gene to a boy who will not have hemophilia.
NHGRI Clinical Research on Hemophilia
Currently, NHGRI is not conducting any clinical research on hemophilia.
Additional Resources for Hemophilia
- Hemophilia A [ncbi.nlm.nih.gov]
- Hemophilia B [ncbi.nlm.nih.gov]
- Hemophilia A [ncbi.nlm.nih.gov]
NCBI information page on hemophilia
- Hemophilia [ghr.nlm.nih.gov]
Genetics Home Reference
From Medline Plus
- Hemophilia [nhlbi.nih.gov]
Information from the National Heart, Lung, and Blood Institute (NHLBI)
- Hemophilia [rarediseases.info.nih.gov]
Information from the Genetics and Rare Diseases Information Center.
- National Hemophilia Foundation (NHF) [hemophilia.org]
Dedicated to finding better treatments and cures for bleeding and clotting disorders and to preventing the complications of these disorders through education, advocacy and research.
- Finding Reliable Health Information Online
A listing of information and links for finding comprehensive genetics health information online.
Last Updated: September 27, 2011