Coagulation Disorders USMLE Step 1 Practice Question
A 62-year-old woman with newly diagnosed adenocarcinoma of the lung completed her second cycle of chemotherapy 2 weeks ago. She presents to the emergency department with acute dyspnea, pleuritic chest pain, and unilateral leg swelling that developed over 2 days. Vital signs: BP 128/82 mmHg, HR 112 bpm, RR 22/min, SpO2 88% on room air, temperature 37.2°C. Laboratory values show: PT 12 seconds (normal 11-13.5), aPTT 28 seconds (normal 25-35), platelet count 185,000/μL, D-dimer 2500 ng/mL (normal <500). CT pulmonary angiography confirms bilateral pulmonary emboli with right lower lobe wedge-shaped infarction. Which of the following mechanisms most directly explains the hypercoagulable state underlying this patient's thromboembolism?
Answer choices
- ALoss of protein C production by malignant hepatic infiltration
- BAcquired antithrombin III deficiency from urinary losses
- CTissue factor and cancer procoagulant released by tumor cells activating the extrinsic pathwayCorrect answer
- DProthrombin gene G20210A polymorphism increasing prothrombin levels
- EFactor V Leiden mutation impairing activated protein C inactivation
- FDecreased plasminogen activator inhibitor-1 production by endothelial cells
See the full explanation
Get the correct-answer rationale, why each distractor is wrong, the underlying mechanism, and high-yield associations — plus adaptive practice that targets your weak areas — with a free MedBoardPRO account.