For most individuals the word hemophilia is at least a recognizable term. Many negative perceptions arise with this bleeding disorder including deep dark family secrets, profuse bleeding from small wounds, excruciating pain, and early death. By definition, hemophilias represent any of a group of disorders in which a particular clotting factor is decreased. With 13 clotting factors necessary for clot formation, there should be a wide range of hemophilias. Classically, however, only two disorders are referred to by the name hemophilias: hemophilia A, factor VIII deficiency and hemophilia B, factor IX deficiency. Both of these disorders are sex-linked recessive disorders, meaning that the mother carries the abnor-
mal gene and passes the gene to her sons. Not every male child will be affected, only those who inherit the abnormal gene. Likewise, if daughters inherit the abnormal gene, they are obligatory carriers. History is rich with accounts of hemophilia from the Talmud to British monarchy. Queen Victoria carried the abnormal gene and passed it through her offspring (nine births, five living children) into the Russian royal family, the Spanish dynasty, and the German royal family (Fig. 17.1). Victoria herself had no family history of hemophilia so her abnormal gene was acquired as a result of spontaneous mutation, which occurs in 30% of cases.
Factor VIII is the only one of the clotting factors that is not synthesized exclusively by the liver. It is unique among clotting factors for two reasons. Factor VIII is genetically controlled by the X chromosome (it is sex-linked), and it forms a complex with von Willebrand factor (vWF), which transports the factor into the circulation and is synthesized by an autosomal chromosome (Fig. 17.2). This clotting factor is also labile and unstable in stored plasma. In individuals with hemophilia A, the vWF level will be normal so that bleeding time will be normal; however, the aPTT will be abnormal because of the reduced level of factor VIII.
Clotting factors are measured in terms of their percent activity as well as their function in coagulation tests. Most clotting factors need to be available in the body at a minimum of 30% to achieve hemostasis. Bleeding manifestation in hemophilia A individuals are related to the level of factor VIII. There are three levels of clotting factor activity in hemophilia:
Patients with severe hemophilia A will manifest early bleeding manifestations such as circumcisional bleeds or umbilical cord bleeding. As they become more mobile, ordinary activities such as crawling, walking, or running may present challenges. It is not uncommon to see the severe hemophiliac child in protective gear (knee pads, ankle pads, helmet) for outside play. Bleeding may occur in other areas such as the gastrointestinal tract, the kidneys (hematuria), or gums or in hematomas. It is not accurate to say that individuals with hemophilia bleed more profusely. Rather, bleeding continues for a longer period of time due to the ro o o
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