- Hemophilia A is the most common inherited bleeding disorder and is caused by a congenital deficiency of coagulation Factor VIII. It is inherited in a X-linked recessive pattern and depending on the mutation can yield mild to severe bleeding, especially the joints
- Mutations of Factor VIII are inherited in an X-linked recessive pattern although spontaneous mutations are also relatively common. Depending on the particular mutation, the degree of Factor VIII deficiency may be more or less profound, yielding a range of possible clinical severity.
- In mild to moderate cases, disease may manifest as an increased susceptibility to bruising with mild trauma or significant hemorrhage following operative procedures. In severe cases, patients tend to develop spontaneous bleeding into large joints, yielding recurrent hemarthroses that over time result in significant joint deformity. Because platelets are unaffected patients with Hemophilia A do not display petechiae.
- Because Factor VIII acts within the intrinsic arm of the coagulation cascade, patients with Hemophilia A display an abnormally long PTT.
- An easy way to remember that Hemophilia A is caused by Factor VIII deficiency is to say the word "Eight" as if it has an "A" at the beginning of it: Ayyyy-ight.