Patient with hemophilia A have bleeding disorder because of
Hemophilia A
X - linked disorder

90% cases - deficiency of factor 8
10% cases functional defect of factor 8

Factor VIII a complex is the most important activator of factor X required for conversion of prothrombin to thrombin.
Lack of platelet count
Lack of platelet adhesion
Lack of factor VIII a during activation of factor X in coagulation coscade
Release of thromboxane A2