A 32-year-old woman develops deep vein thrombosis during her second pregnancy. Testing shows resistance to activated protein C. The underlying mutation alters which factor?

• A Factor V Arg506Gln mutation ✓
• B Prothrombin G20210A mutation
• C Methylene tetrahydrofolate reductase mutation
• D Factor II prothrombin gene promoter mutation

Explanation

Factor V Leiden is a single nucleotide change replacing arginine 506 with glutamine at one of the activated protein C cleavage sites on factor Va. Mutant Va resists proteolytic degradation by activated protein C, producing activated protein C resistance, the commonest inherited thrombophilia in Caucasian populations. Prothrombin G20210B raises prothrombin levels but does not cause APC resistance.

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.