F10 and hemophilia A: FVIIIa acts as a cofactor for activatedfactor IXa (FIXa), forming the intrinsic tenase complex, which catalyzesthe cleavage of factor X (FX) to form activated factor X (FXa) andamplify thrombin production.3,7,8 Disruption of FVIII expression and/or function due to genetic mutationcauses congenital hemophilia A, an X-linked bleeding disorder thataffects 1 in 5000 male births.9 Of these,missense mutations can affect various FVIII procoagulant functions,such as binding to vWF, FIXa, and activated platelet surfaces.10