The pathophysiology of hemophilia covers a sex-linked inherited coagulation disorder caused by the reduced levels of plasma glycoproteins including the coagulation factor VIII (FVIII) leading to the development of hemophilia A and the analogous reduced levels of coagulation factor IX (FIX) leading to the development of hemophilia B (Christmas disease) [1]. The gene discussed is F8; the disease is blood coagulation disease.