What is Hemophilia?
- Hemophilia is an inherited bleeding disorder. The blood of someone with hemophilia will not clot normally. Bleeding may occur spontaneously or following injury.
- Hemophilia occurs in 2 forms, hemophilia A and B. In both forms, a gene is defective. The defective gene interferes with the ability of the body to produce the clotting factors that allow for normal clotting. The result is a tendency for abnormal, excessive bleeding.
- With either disorder, you may show a mild form in which bleeding occurs only under severe stress, such as major injury.
- Moderate cases rarely will have spontaneous bleeding but will bleed after surgery or trauma.
- Severe cases will exhibit spontaneous bleeding-that is, bleeding without any recognizable trauma. Spontaneous bleeding can occur in any part of your body, but it is usually in the joints of the fingers, wrists, feet, and spine.
Hemophilia A and B Causes
- Men have only one X chromosome. If that chromosome carries the abnormal hemophilia gene, the man will have the disease hemophilia. Both hemophilia A and B are linked to the X chromosome, which means they primarily affect men.
- Women have two X chromosomes. Even if one of the X chromosomes carries the defective gene, the normal gene on the other X chromosome will protect the woman from hemophilia. The gene does not affect them, but they carry it and pass it on to their children.
- If a woman is a carrier, she has a 50% chance that her sons will have hemophilia. Likewise, she has a 50% chance that her daughters will be carriers of hemophilia. This assumes that the woman's partner is not a hemophiliac.
- A man who has hemophilia has a 100% chance that his daughters will be carriers, since they must inherit the defective x chromosome from the father. His sons will not be affected if the mother is not a carrier.
- The transmission of this gene to offspring accounts for most cases of hemophilia. The remaining cases occur from spontaneous changes in genes responsible for causing hemophilia.
Medically Reviewed by a Doctor on 2/11/2016
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