An 18-year-old man with a medical history significant for a bleeding disorder presents for evaluation of easy bruising. He denies experiencing any bleeding at this time. Results of todays laboratory evaluation are as follows: leukocyte count, 6,000; Hb, 13; platelets, 200,000; prothrombin time, 13 sec; and PTT, 70 sec. His repeat PTT was 67 sec. A mixing study was performed with correction of the PTT.
Which of following is the most likely diagnosis?
A. Factor VIII deficiency B. Lupus Anticoagulant C. Factor VIII inhibitor D. Glanzmann thrombasthenia E. None of the above
Factor viii deficiency-a prolonged clotting time (e.g., aptt of 60 seconds [normal, 28 to 30 seconds]) can be caused by either a clotting factor deficiency or an inhibitor. an inhibitor is generally an antibody directed against a specific clotting factor or against a phospholipid-protein complex, the so-called lupus anticoagulant. in a mixing study, one volume of a patients plasma is mixed with an equal volume of normal plasma. the resulting mixture provides at least 50% of a deficient factor and corrects the abnormality. if the problem is caused by an inhibitor, the resulting plasma mixture still has a prolonged clotting time. a mixing study should always be done when a prolonged clotting time is noted.