PT which measure the activity of extrinsic pathway of coagulation cascade is not affected in hemophilia. In hemophilia aPTT which measure the intrinsic coagulation cascade activity is prolonged, and is associated with normal bleeding time and platelet count. Hemophilia is an X linked disorder of coagulation caused by the deficiency in a circulating plasma protein. Hemophilia A is caused by the deficiency of factor VIII, and hemophilia B is caused by the deficiency of factor IX. Bleeding is the common manifestation of hemophilia and the common bleeding manifestations are hemahoses, hematomas, mucocutaneous bleeding, intracranial bleeding, hematuria and pseudotumor. Ref: Harrison's Principle of Internal Medicine, 16th Edition, Page 680