Hemophilia is a rare bleeding disorder in which the blood does not clot normally. People with hemophilia have little or no blood clotting factors, which are needed for normal blood clotting.
There are two types of hemophilia:
- Hemophilia A is also known as classic hemophilia because it is the most common. Clotting factor VIII (eight) is low or missing in hemophilia A.
- Hemophilia B may also be referred to as Christmas disease. Clotting factor IX (nine) is low or missing in hemophilia B.
Hemophilia is inherited – it is passed on from parents to children. In rare cases, a child may be born to a family that has no history of hemophilia. This may be due to an unknown family history of hemophilia or due to a random, new mutation (an abnormal change) in genes carrying hemophilia.
In Canada, hemophilia A affects about 1 in 10,000 people. Hemophilia B is less common, affecting about 1 in 50,000 people. Hemophilia affects people of all races, colours, and ethnic backgrounds.
The most severe forms of hemophilia usually affect males only. Females may have severe hemophilia in certain instances, such as if the father has the disorder and the mother is a carrier. A carrier has the abnormal hemophilia genes but usually does not have the signs or symptoms of hemophilia. In some cases, women who are carriers may have symptoms of mild hemophilia.