Coagulation and Hemophilia Greater Independence
Hemophilia is a genetic bleeding disorder. People who have hemophilia have a deficiency or an absence of a coagulation protein. A blood clotting factor is deficient or absent. Bleeding is most often into joints, such as the knee, elbow, or ankle, but bleeding can occur anywhere in the body. People with hemophilia bleed longer, not faster. The severity of hemophilia varies greatly. Hemophilia A and Hemophilia B are the most common genetic bleeding disorders. Hemophilia A is observed in 80 percent of hemophiliacs and is a deficiency or absence of Factor VIII. It can also be referred to as "classic" hemophilia. In the second most common, hemophilia B, factor IX is missing. This is also known as the "Christmas Disease" because of the surname of the first patient studied. Hemophilia was identified as early as biblical times. Doctors in medieval times were familiar with it as well. In 1803, a Philadelphia doctor published the first description of hemophilia in the United States. But it was not until 30 years later that hemophilia became widely recognized. Hemophilia later developed a reputation as the "royal disease" because it passed from Queen Victoria of England to her descendants throughout the royal houses of Europe. About eighty percent of all cases of hemophilia have an identifiable family history of the disease; in other instances, it may be attributable to a spontaneous mutation. Researchers recently discovered that the spontaneous mutation of the factor VIII gene in two children was due to the attachment of a foreign "jumping gene" that disrupted the blood-clotting ability of the factor VIII gene. Inheritance is controlled by a recessive sex-linked factor carried by the mother on the X chromosome. A probability of one in two exists that each boy born to a normal male and a carrier female will be hemophiliac and the same chance that each girl of this union will be a carrier. Of the children of a hemophiliac male and a normal female, all the
Cited: Louis Levine, B.S., M.S.Ed., A.M., Ph.D. Professor, Department of Biology, City College of New York. "Hemophilia," Microsoft® Encarta® Online Encyclopedia 2000 http://encarta.msn.com © 1997-2000 Microsoft Corporation. All rights reserved.