What Is It?

Hemophilia is an inherited (genetic) disorder that prevents blood from clotting properly. Clotting means the blood thickens or congeals. This keeps a cut from bleeding endlessly by forming a scab. People with hemophilia bleed longer than usual. This bleeding can range from mild to severe. In severe cases, people with hemophilia can bleed to death.

People with hemophilia do not have enough clotting factors, parts of the blood that help bleeding stop. This condition is caused by a defect in the DNA. DNA is the genetic code you inherit from your parents. It defines your eye color, height and much more.

In the United States, about 17,000 people have hemophilia. It is almost exclusively a male disease. Females can get it, but it is very rare. Why is this a “male” disorder? Here’s a quick lesson in genetics:

All people have 23 pairs of chromosomes, which are coiled pieces of DNA. Women have two X chromosomes. Men have one X chromosome and one Y chromosome. Hemophilia is caused by defects in X chromosomes. If a woman has a defect on one X chromosome, she can fall back on her other (unaffected) X chromosome and not develop hemophilia. Because a man has only one X chromosome, if he has a defect on it, he has no other X chromosome to rely on.

Women with one defective X chromosome and one normal X chromosome are carriers of hemophilia. In the very rare cases in which a woman gets hemophilia, it’s because she inherited two defective X chromosomes, one from her mother (a carrier) and one from her father (who has hemophilia).

In most cases, the defective gene that leads to hemophilia is passed down through several generations, but in about 20 percent of cases, the defect arises as a spontaneous mutation (a new DNA defect) in the parent or affected child.

Hemophilia A and B are the two most common types of hemophilia.

  • Hemophilia A is the most common type of hemophilia, occurring in about 80 percent of people with the disorder. People with hemophilia A do not have enough clotting factor VIII (8), which is caused by a DNA defect on the X chromosome that produces deficiencies in factor VIII.

    The extent of the bleeding problem relates to the amount of coagulation factor the person has. People with levels less than 1 percent of the normal amount of coagulation factor have severe disease. People with 1 percent to 5 percent of normal levels have moderate disease, and people with more than 5 percent of normal levels have mild disease. Two-thirds of people with hemophilia A have severe disease.

  • Hemophilia B, also known as Christmas disease (named after the family in whom it was first diagnosed), accounts for 12 percent to 15 percent of hemophilia cases. Caused by a deficiency in coagulation factor IX (9), hemophilia B is linked to an inherited problem on the X chromosome. It can be mild, moderate or severe. People with hemophilia B are less likely to have severe disease than people with hemophilia A: About half of people with hemophilia B have mild or moderate disease.

Factor XI deficiency is another type of coagulation disorder. Caused by a deficiency in coagulation factor XI (11), is not inherited on the X chromosome. This means bleeding problems can be passed to both male and female children, and that either parent may be a carrier. A child who inherits the problem from only one parent usually has high enough levels of coagulation factor XI to prevent significant bleeding. However, a child who inherits the problem from both parents may have only 1 percent to 10 percent of normal factor XI levels, which may produce significant bleeding.


People with hemophilia may bleed anywhere throughout the body, but they seldom bleed from small cuts or puncture wounds, such as from the needles used to draw blood. They bleed more than other people do from significant injuries, trauma or surgery. Eighty percent of the time, they bleed into joints (hemarthroses), usually the ankle, knee or elbow. The affected joint becomes warm, painful and swollen, and the person is not able to move the joint as freely as before. This can happen spontaneously or after an injury.

Bleeding into muscle (hematomas); the esophagus, stomach or intestine (gastrointestinal bleeds); the urine (hematuria); from the nose and gums, and heavy menstrual bleeding are also common. A less common, but more serious complication is bleeding into the brain (intracranial), which occurs in about 12 percent of children with severe hemophilia. Symptoms include the sudden development of nausea, headache and a decrease in mental awareness.

How bad and how often people bleed is in proportion to how much coagulation factor they have. People with severe hemophilia often develop bleeding problems within the first two years of life. Many infants are diagnosed when they suffer prolonged bleeding after circumcision. Others are diagnosed after they develop excessive bruising and bleeding into joints following typical childhood injuries. People with mild hemophilia may not be diagnosed for decades, and only after they experience abnormal bleeding after trauma, injury or surgery.

In general, symptoms of factor XI deficiency usually appear only in patients who inherit two defective chromosomes (one from each parent). These symptoms can include prolonged and/or excessive bleeding after cuts, surgery or dental extractions; nosebleeds (epistaxis); blood in the urine (hematuria); and (in girls) abnormally heavy or prolonged menstrual bleeding. Unlike hemophilia A and B, spontaneous bleeding is rare.


If your doctor suspects that you have hemophilia, he or she will ask how often you bleed and how severely. Your doctor will also ask if anyone in your family has a bleeding problem. In most cases, the person’s mother will have a family member with a bleeding problem. Your doctor will examine you, focusing on evidence of past bleeding into the skin, muscles and joints. A variety of blood tests will show if your blood has a coagulation defect. If you have a clotting defect, the diagnosis of hemophilia A or B or factor XI deficiency can be confirmed by examining specific clotting factors.

Expected Duration

Hemophilia is a lifelong illness. Symptoms usually can be controlled with proper medical treatment.


People with a family history of hemophilia can talk to a genetic counselor to learn their risks of passing hemophilia on to their children. A simple blood test is usually all that is necessary.

People with hemophilia can help prevent episodes of bleeding by avoiding injuries, accidents and excessive strain on the joints. An infant with hemophilia should have appropriate padding in his crib or playpen, and he should be supervised as he learns to walk. In school, he should avoid contact sports and physical education activities that have a high risk of trauma. Instead, encourage the child to participate in walking and swimming, though he should avoid the diving team.

You can decrease the risk of joint damage significantly through preventative treatment. This means using coagulation factor concentrates, starting early in life. These products help decrease how often and how severely you bleed. People with hemophilia must avoid aspirin and other medications that affect blood coagulation.

Because people with hemophilia may need a blood transfusion at some point, you should be immunized against hepatitis A and B, disease that can be carried in blood products.


When a person with hemophilia has a bleeding episode, it often can be controlled with blood plasma that contains all of the clotting factors (hemophilia A, hemophilia B or factor XI deficiency), or an infusion of factor VIII (for hemophilia A) or factor IX (for hemophilia B). For people with mild hemophilia A, desmopressin (DDAVP or Stimate) also can be used to increase the person’s own factor VIII level.

Hospital treatment is necessary when bleeding occurs. The situation is an emergency when it involves the brain, neck, any component of the central nervous system and any vital organs. All surgical or invasive procedures should be done in a hospital to properly handle bleeding. Consult your doctor before having dental work.

When To Call A Professional

If you are a parent, call your doctor whenever you notice unexplained or severe bruises on your child’s body, or a warm, painful joint. If you are an adult and you experience these symptoms, call your doctor.


How well you do depends on the type of hemophilia and its severity. In the 1950s, 60 percent of males with severe hemophilia A did not live to become adults. Today, thanks to the development of coagulation-factor products, most people with hemophilia can look forward to a near-normal lifespan.

There are three main complications that may develop in hemophiliacs:

  • Joint destruction — Many people with hemophilia develop severe joint damage from multiple episodes of bleeding into joints (hemarthroses).

  • Blood-borne infection — In the ‘70s and early ‘80s, many hemophiliacs developed hepatitis C, and up to half developed HIV. However, with improved testing and purification techniques, it is now exceedingly rare for these infections to be transmitted.

  • Development of inhibitor antibodies — About 25 percent of people with severe hemophilia A and up to 5 percent of people with severe hemophilia B who are treated with coagulation factors will develop inhibitor antibodies. These are infection-fighting proteins that decrease the effectiveness of the clotting treatment. When this occurs, treatment can be complicated and expensive.

Johns Hopkins patient information

Last revised:

Diseases and Conditions Center

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All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.