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 girls will be carriers and all the boys will be normal. Males cannot transmit the disability, and female carriers are free of the disease. Conventional wisdom suggests that 1 in 10,000 males in the United States have hemophilia. However, increased research and focus, on bleeding disorders in general and on bleeding disorders in women specifically, suggest a shift in what is known about who has a bleeding disorder. Clotting factor is one of 12 or more proteins found in blood that work together to make blood clot. They are designated by Roman numerals I through XIII. When the body detects bleeding, clotting factors are switched on in a specific order, each sending an activating message to the next. Factor VIII is one of the clotting factor proteins that helps produce the fibrin clot. Sufficient quantities of fibrin must be made by the body in order for fibrin to act like a net that holds the platelets together to make a firm blood clot. In persons with hemophilia A, fibrin is not made properly, so firm blood clots do not form in the wound, and bleeding continues. There are two major processes involved in blood clotting. The first part has to do with platelets. They are like little shingles which go to where a blood vessel has ruptured, and they stick over the hole and make a plug. This is the first step of making a clot. The plug is only temporary, and the platelets can easily fall off. The platelets soon rupture and release chemicals that attract more platelets and make them "sticky", too. The chemicals released by the rupturing platelets also activate various clotting factors which are proteins in the blood. The next step is that fibers form from the activated proteins and mix with the platelets. The fibers are like a net, or a weave of yarn, and they make the clot stronger. The substance that makes the fibers is called fibrinogen. There are twelve factors which work together to make the fibrinogen. People with hemophilia have a problem with one or...
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.
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