HEMOPHILIA A - A sex-linked genetic disease [affecting males] that results from a deficiency of clotting factor VIII, a protein factor that is required for normal blood coagulation. Symptoms include easy bruising, bleeding gums, nosebleeds, and bleeding into muscle tissue (hematoma) or a joint space (hemarthrosis). Treatment includes the infusion of factor VIII concentrate intravenously to restore this essential factor and normalize blood coagulation.