A genetically inherited bleeding disorder characterized by inadequate amounts of clotting factor VIII in blood plasma. Factor VIII deficiency is the cause of the bleeding disorder known as hemophilia A. Factor VIII, also known as antihemophilic factor (AHF), is a substance involved exclusively in blood coagulation (clotting). Factor VIII deficiency is inherited as a sex-linked recessive trait; only males can inherit the disorder. Females may carry the disorder and pass it on to their sons; their daughters can also be carriers. All daughters of affected males are carriers, but men cannot pass the disease on to their sons.