Pathophysiology
The basic defect of hemophilia A is deficiency of factor VIII (antihemophilic factor [AHF]). AHF is produced by the liver and is necessary for the formation of thromboplastin in phase I of blood coagulation. The less AHF found in the blood, The more severe the disease. Individuals with hemophilia have two of the three factors required for coagulation: vascular influence and platelets. Therefore they may bleed for long periods, but not at a faster rate.
Bleeding into subcutaneous and intramuscular tissue is common. Hemophilia, which is bleeding into a joint space, is the most frequent type of internal bleeding. Bony changes and crippling deformities occur after repeated bleeding episodes over several years. Signs of hemarthrosis are swelling, warmth, redness, pain, and loss of movement. Bleeding in the neck, mouth, or thorax is serious because the airway can become obstructed. Intracranial hemorrhage can have fatal consequences and is one of the major causes of death. Hemorrhage anywhere along the GI tract can lead to anemia, and bleeding into the retroperitoneal cavity is especially hazardous because of the large space for blood to accumulate. Hematomas in the spinal cord can cause paralysis