Hemophilia
Hemophilia, hereditary blood disease characterized by the inability of blood to clot, or coagulate, leading to hemorrhage , or excessive bleeding, even from minor injuries. The disease is caused by an insufficiency or absence of certain blood proteins , called factors, that participate in blood clotting. The most common form, hemophilia A, is observed in 80 percent of hemophiliacs and is caused by a lack of factor VIII; in the second most common, hemophilia B (Christmas disease), factor IX is missing. The severity of hemophilia varies greatly. The bleeding may occur as excessive bruising or persistent bleeding after a simple cut. Hemorrhaging into joints and muscles can be disabling. Before the advent of modern therapy, the chance of survival to adulthood was poor. About 80 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 of genes . Researchers recently discovered that the spon...