Feline factor XII (Hageman) deficiency.

A coagulation profile from a clinically normal female cat revealed an intrinsic coagulation defect characterized by prolonged activated partial thromboplastin time, with normal bleeding time, platelet count, and prothrombin time. Subsequent correction studies, utilizing activated partial thromboplastin time, confirmed factor XII deficiency. Hematologic and clinical studies on the cat failed to reveal an underlying disease process that might result in acquired factor XII deficiency.