Hemophilia A: A Genetic Disorder
Created | Updated Jan 28, 2002
Hemophilia A is a genetic disorder in which the clotting properties of blood are lost. Due to a lack of a specific protein in the blood's serum, hemophiliacs may experience easy bleeding from the nose, intestinal tract, and kidneys; swelling and oozing of blood deep under the skin or in muscles upon mild injury; bleeding into joints, causing deformities; or hematomas: large accumulations of blood under the skin.
In order to form a blood clot, red blood cells mesh into thin threads of fibrin. This protein is produced when thrombin, fibrinogen, and calcium ions interact. Ten other chemical factors are required in order to form a blood clot. Scientists have isolated a lack of factor VIII in the clotting process as the cause of hemophilia, as well as a decreased formation of thromboplastin, and a diminished conversion of prothrombin during the clotting process.
Factor VIII is normally present in blood plasma and in concentrations from this plasma. Although healthy blood transfusions are not helpful, plasma injections seem to help control hemorrhaging. Some hemophiliacs are able to anticipate a bleeding episode and can thereby pre-treat themselves with plasma.
Hemophilia A afflicts one out of ten thousand males in the United States. The hemophilia A gene is carried on the X chromosome; it is recessive to the normal X chromosome, but is dominant to the Y chromosome. Since the normal X chromosome has a gene that counteracts the effect of the hemophilia A gene, only males are affected. This is because the Y chromosome is too small to carry the counteracting gene.
In order to form a blood clot, red blood cells mesh into thin threads of fibrin. This protein is produced when thrombin, fibrinogen, and calcium ions interact. Ten other chemical factors are required in order to form a blood clot. Scientists have isolated a lack of factor VIII in the clotting process as the cause of hemophilia, as well as a decreased formation of thromboplastin, and a diminished conversion of prothrombin during the clotting process.
Factor VIII is normally present in blood plasma and in concentrations from this plasma. Although healthy blood transfusions are not helpful, plasma injections seem to help control hemorrhaging. Some hemophiliacs are able to anticipate a bleeding episode and can thereby pre-treat themselves with plasma.
Hemophilia A afflicts one out of ten thousand males in the United States. The hemophilia A gene is carried on the X chromosome; it is recessive to the normal X chromosome, but is dominant to the Y chromosome. Since the normal X chromosome has a gene that counteracts the effect of the hemophilia A gene, only males are affected. This is because the Y chromosome is too small to carry the counteracting gene.
