A healthy 20-year-old woman has a persistently prolonged aPTT of 75 seconds discovered on routine preoperative testing. PT, platelet count, bleeding time and TT are normal. She has never had any abnormal bleeding, including two dental extractions and an appendectomy. Mixing study fully corrects with normal plasma. The most appropriate conclusion is:
- A She has mild von Willebrand disease and needs desmopressin before surgery
- B She has a lupus anticoagulant and should receive anticoagulation before surgery
- C She has factor XII deficiency, which does not cause clinical bleeding, and needs no hemostatic treatment ✓
- D She has occult hemophilia C and should receive fresh frozen plasma
Correct answer: C. She has factor XII deficiency, which does not cause clinical bleeding, and needs no hemostatic treatment
Explanation
Factor XII (Hageman factor) initiates the intrinsic pathway in vitro but is not required for physiologic hemostasis in vivo, so its deficiency prolongs aPTT without any bleeding tendency. Correction on mixing excludes an inhibitor such as lupus anticoagulant, which would also be associated with thrombosis rather than bleeding. Von Willebrand disease prolongs bleeding time, and factor XI deficiency (hemophilia B) typically does cause bleeding after surgery or trauma.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.