Hemophilia A is due to decreased activity of which factor and is X linked?

Hemophilia A is due to decreased activity of which factor and is X linked?

• A. Factor IX
• B. Factor X
• C. Factor II
• D. Factor VIII

Answer: (D)

Factor VIII deficiency defines Hemophilia A. Factor VIII acts as a cofactor for activated factor IX (IXa) in the intrinsic pathway, forming the tenase complex that activates factor X and drives thrombin generation. When factor VIII activity is low, this pathway stalls, leading to impaired clot formation and a bleeding tendency, especially into joints and muscles. The condition is X-linked, so it predominantly affects males, with females typically carriers. This distinguishes it from Hemophilia B, which is due to factor IX deficiency, and from deficiencies of other factors that affect different steps of the cascade.

Factor VIII deficiency defines Hemophilia A. Factor VIII acts as a cofactor for activated factor IX (IXa) in the intrinsic pathway, forming the tenase complex that activates factor X and drives thrombin generation. When factor VIII activity is low, this pathway stalls, leading to impaired clot formation and a bleeding tendency, especially into joints and muscles. The condition is X-linked, so it predominantly affects males, with females typically carriers. This distinguishes it from Hemophilia B, which is due to factor IX deficiency, and from deficiencies of other factors that affect different steps of the cascade.