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Updated: Dec 21 2021

Factor V Leiden

Images
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  • Snapshot
    • A 30-year-old Caucasian man presents with sudden shortness of breath. He denies any recent long train or plane rides, but endorses a history of multiple DVTs. A Doppler ultrasound shows a small DVT in his left calf. His complete blood count is normal. His PT and PTT are also normal. He is started on LMWH with the intention of bridging to warfarin. A few days later, his activated protein C resistance assay comes back positive for a factor V Leiden mutation.
  • Overview
  • Introduction
    • Hypercoagulable state/thrombophilia from mutated factor V
  • Epidemiology
    • Most common cause of inherited hypercoagulable states
    • Most common in Caucasians
  • etiology
    • Pathogenesis
      • review of anticoagulation pathway
        • protein C (with protein S as a co-factor) inactivates factors V and VIII
      • mutated factor V lacks cleavage site for activated protein C
        • factor V remains active in coagulation pathway
        • defective anticoagulation
        • thrombosis
    • Genetics
      • factor V Leiden mutation
      • incomplete autosomal dominant
        • heterozygous → risk of thrombosis
        • homozygous → higher risk of thrombosis
  • Presentation
    • Symptoms/physical exam
      • most common
        • DVT, recurrent
      • less common
        • PE
        • central retinal vein occlusion
        • hepatic vein thrombosis
      • if pregnant
        • higher risk of miscarriage
  • STUDIES
    • Normal PT/PTT
  • Differential Diagnosis
    • Protein C/S deficiency
    • Malignancy
    • HIT
    • Antiphospholipid syndrome
    • Antithrombin deficiency
      • presents with no change in PTT with heparin administration
      • treat with direct thrombin inhibitor (or very high dose heparin) followed by warfarin
  • Diagnosis
    • Activated protein C resistance assay (factor V Leiden specific functional assay)
    • if positive, confirm with DNA testing
  • Treatment
    • Prevention
      • avoid external causes of hypercoagulability
        • OCPs
        • hormone replacement therapy
    • If thrombosis
      • LMWH bridge to warfarin
    • If pregnant, give thromboprophylaxis
      • LMWH
      • warfarin contraindicated
    • Long-term antithrombotic therapy not recommended
  • Complications
    • Miscarriage
    • Thrombosis
  • Prognosis
    • Mortality not affected
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