What is the primary genetic defect associated with Hemophilia A?

Hemophilia A is primarily characterized by a deficiency in Factor VIII, a crucial protein in the blood coagulation process. This deficiency leads to the inability of blood to clot properly, resulting in prolonged bleeding and difficulty controlling bleeding episodes.

Factor VIII plays a vital role in the intrinsic pathway of the coagulation cascade; it interacts with Factor IXa to activate Factor X, which is essential for converting prothrombin to thrombin during the clotting process. Without adequate levels of Factor VIII, patients with Hemophilia A experience bleeding tendencies, especially after injuries or surgeries, and may also have spontaneous bleeding episodes.

The other options highlight different conditions or deficiencies. For example, Factor IX deficiency is associated with Hemophilia B, von Willebrand factor deficiency causes von Willebrand disease, and Factor V deficiency is linked to a separate clotting disorder known as parahemophilia. Each of these is distinct from Hemophilia A, which is specifically defined by the lack of Factor VIII.