Clinical and pathological aspects of hemophilia a in Japanese Brown cattle.

A coagulopathy with subcutaneous bleeding and muscular or peritracheal/periesophageal bleeding occurred in two male Japanese Brown calves of the same dam. One of the affected calves died three days after the onset of bleeding and the other survived normally until being slaughtered despite once suffering from subcutaneous hematoma. Hemostatic tests of the latter case showed prolonged activated partial thromboplastin time (APTT), and severely reduced factor VIII activity. In addition, von Willebrand factor activity, determined by the human platelet aggregation test, was within the normal range; therefore, the calf was diagnosed with hemophilia A. These are the first bovine cases of hemophilia A definitely diagnosed clinicopathologically.