A 53-year-old woman arrives at the hospital with bleeding into the back of the throat and has a coagulation screen performed

She has no history of abnormal bleeding before this despite major stress to hemostasis in the past: she was in a major automobile accident at age 37 and has had impacted wisdom teeth extracted. Her coagulation results follow:

Patient's Results Reference Range 1:1 Mix with Normal Plasma
Prothrombin time (PT) 13.1 seconds 11-15 seconds
Partial thromboplastin time (PTT) 87 seconds 25-37 seconds 35
Fibrinogen 380 mg/dL 200-400 mg/dL

Which of the following is the most likely cause for her bleeding?

a. Factor XII deficiency
b. Factor IX deficiency
c. Factor VIII deficiency
d. Factor VIII inhibitor

ANS: D
This patient is bleeding abnormally. However, she has had major trauma in the past with no abnormal bleeding; this suggests the problem is acquired, not congenital. The PTT is prolonged, so the common pathway appears to be intact. The prolonged PTT fully corrects on a 1:1 mix, although at the upper end of the reference range. Putting all of this together, the most likely problem is an acquired factor VIII inhibitor.