Question

A genetic defect in coagulation factor IX causes hemophilia b, a disease characterized by a tendency to bleed profusely after very minor trauma. However, a genetic defect in coagulation factor XI has only mild clinical symptoms. Explain this discrepancy in terms of the mechanism for activation of coagulation protease.

Answer 1

Answer:

• Hemophilia B also called factor IX deficiency or Christmas disease.
• It is a genetic disorder caused by missing or defective factor IX , a clotting protein, although it is passed down from parents to children by a spontaneous mutation, a change in the gene.
• Hemophilia is a disorder in which blood doesn't clot normally.
• When blood can't clot properly, excessive bleeding( external and internal) occurs after any injury or damage.
• Symptoms include many large or deep bruises, joint pain and swelling ,unexplained bleeding and blood in urine or stool.
• Treatment includes injections of a clotting factor or plasma.
• In some number of people with hemophilia who have had liver transplants, their hemophilia has been cured. This is because clotting factor is made in the liver.
• Hemophilia A and B are inherited as X- linked recessive genetic disorders.
• Therefore, hemophilia A and B are fully expressed in males only.
• Proteases in blood clotting - blood coagulation is initiated by exposure of tissue factor, which forms a complex with factor VIII and factor X , which results in the generation of small quantities of thrombin and is rapidly shutdown by the tissue factor pathway inhibitor.

Hemostasis involves three basic steps:

• Vascular spasm, the formation of a platelet plug, and coagulation in which clotting factors promotes the formation of a fibrin clot.
• Fibrinolysis is the process in which a clot is degraded in healing vessel. Anticoagulants are substances that oppose coagulation.
• Calcium binds to the phospholipids that appear secondary to the platelet activation and provides a surface for assembly of various coagulation factors.

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