A 28-year-old woman presents with her first episode of deep vein thrombosis. She has no obvious risk factors. Laboratory testing shows resistance to activated protein C (APC resistance). Genetic testing confirms a mutation in the factor V gene. What is the molecular mechanism by which factor V Leiden causes thrombophilia?
- A Factor V cannot be activated by thrombin
- B Factor V Leiden has increased binding to tissue factor
- C Factor V Leiden cannot be cleaved and inactivated by activated protein C ✓
- D Factor V Leiden cannot bind to factor VIII
Correct answer: C. Factor V Leiden cannot be cleaved and inactivated by activated protein C
Explanation
Factor V Leiden has an Arg506Gln mutation at the primary cleavage site for activated protein B. This renders factor V resistant to proteolytic inactivation by APC, so it persists as a procoagulant cofactor, generating excess thrombin. It is the most common inherited thrombophilia in populations of European descent.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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