What is Hemophilia? -- Bleeding Disorders Association of Northeastern New York (BDANENY), Inc.

More than 15,000 people in the United States have hemophilia (either hemophilia A or hemophilia B). A person with hemophilia has a missing or low supply of one of the factors needed for normal blood clotting. Depending on the level of these factors in the blood, hemophilia may be classified as mild, moderate, or severe. About 60% of persons with hemophilia are of the severe type. They are at risk for bleeding after dental work, surgery, and trauma. They also may suffer internal bleeding with no trauma or injury and without apparent cause. Repeated bleeds can lead to other health problems and disabilities, including chronic joint problems and loss of range of motion. About 15% of persons with hemophilia have moderate hemophilia. These people are at risk for bleeding after surgery or trauma, joint problems, and rarely, spontaneous bleeds. Twenty-five percent of people with hemophilia have mild hemophilia. Their disease may be so mild that it may go undetected until bleeding occurs after trauma or surgery.

The hemophilia gene is carried by females on one of their X-chromosomes and may be passed to their male offspring. This is why hemophilia is called an X-linked genetic condition. Female carriers of hemophilia have one X chromosome with a working (normal) gene and one X chromosome with a non-working (defective) gene. There is a 50% chance the carrier will pass the hemophilia gene on to male offspring. In other words, there is a 50% chance that each of her male children will have hemophilia. There is a 50% chance each of her daughters will also be a carrier.

In about a third of all cases, there is no family history of the disease, and hemophilia occurs as a result of a spontaneous gene mutation. In such situations, the presence of the hemophilia gene may only become apparent when the mother is tested for carrier status after giving birth to a son with hemophilia.

Any male who inherits the defective X-chromosome has hemophilia. This is because males, unlike females, have only one X-chromosome. The Y-chromosome is mainly involved in determining gender and does not contain genes for the production of clotting factors. Boys born to a father with hemophilia and a mother who is not a carrier will not have the disease. This is because boys get the X-chromosome from their mother and Y-chromosome from their father. However, all daughters born to men with hemophilia will inherit the father's hemophilia gene. This is because they get one X-chromosome from their mother and one X-chromosome from their father. Thus, they will be carriers.

Some female carriers have no health problems or symptoms related to carrying the hemophilia gene. These women are known as asymptotic carriers. However, other female carriers have low factor levels that are associated with bleeding problems. These symptomatic carriers may suffer excessive nosebleeds, bruising and bleeding after surgery, dental work, or childbirth. Stress, exercise, medication, and changing hormone levels (during menstruation, during and/or after pregnancy) all may affect the bleeding patterns of symptomatic carriers. Female carriers who have excessive bleeding should be evaluated by a doctor skilled in treating bleeding disorders. Local hemophilia agencies can offer information about medical and other community resources.

Reprinted, with permission, of the National Hemophilia Foundation, Inc.