Hemophilia A is an X-linked recessive bleeding disorder caused by a deficiency in the activity of coagulation factor VIII. The disorder is clinically heterogeneous with variable severity, depending on the plasma levels of coagulation factor VIII: mild, with levels 6 to 30% of normal; moderate, with levels 2 to 5% of normal; and severe, with levels less than 1% of normal. Patients with mild hemophilia usually bleed excessively only after trauma or surgery, whereas those with severe hemophilia have an annual average of 20 to 30 episodes of spontaneous or excessive bleeding after minor trauma, particularly into joints and muscles. These symptoms differ substantially from those of bleeding disorders due to platelet defects or von Willebrand disease (193400), in which mucosal bleeding predominates.
Confirmation of a clinical diagnosis, Carrier testing in unaffected family members