A 66-Year-Old Caucasian Man of Italian Decent Was Admitted to the Hospital

A 66-year-old Caucasian man of Italian decent was admitted to the hospital for a grade III draining ulceration and underlying osteomyelitis of the left fifth metatarsal head. Past medical history was significant for Type 1 diabetes. Past surgical history was significant for a resection of an infected tibial sesamoid of the right foot. Prior to treatment of the ulceration routine clotting tests were performed and showed significantly prolonged activated partial thromboplastin (aPTT) time (69.5 second; normal 30-40 second) , while prothrombin time (PT) was normal. Given these findings, which of the following factors of coagulation is most likely to be defective in this patient?

A) factor VII
B) factor XI
C) prekallikrein
D) tissue factor
E) tissue factor pathway inhibitor, TFPI