Factor V Leiden

Aka: Factor V Leiden, Factor 5 Leiden, Factor V Leiden Mutation, Factor V Leiden Heterozygote, Factor V Leiden Homozygote, Activated Protein C resistance, APC Resistance

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II. Epidemiology

  1. Most common inherited Thrombophilia in the United States
    1. HeterozygousPrevalence: 3 to 7% (U.S.)
    2. Responsible for 20-50% of Hypercoagulable patients
  2. Incidence of Autosomal Dominant genetic defect
    1. Europeans: 15%
    2. North America: 3-5%
  3. Ethnicity
    1. Most common in white patients
    2. African Americans represent <1% of cases

III. Pathophysiology

  1. Factor V is a Cofactor for Factor X
  2. Defect prevents Factor V (and Va) degradation by Protein C
  3. Originally named for a poor Anticoagulant response to activated Protein C (APC)

IV. Labs

  1. Activated Protein C (APC) resistance
    1. Can not be anticoagulated when this lab is run
    2. Tests for Anticoagulant response to activated Protein C (APC)
      1. Activated form of Factor V (Factor Va) is more slowly degraded by activated Protein C
      2. Although Factor V Leiden is the most common cause of APC Resistance, it is not the only cause
  2. PCR for Factor V Leiden
    1. Responsible for 95% of APC Resistance
    2. Does NOT require that patient be off Anticoagulation
    3. Patients may be found to be either Heterozygous or Homozygous for Factor V

V. Complications

  1. General
    1. Heterozygote: 5-10 times the risk of thrombosis
    2. Homozygote: 50-100 times the risk of thrombosis
    3. Factor V Leiden is found in 21% of DVT patients (contrast with 5% of healthy patients)
      1. Also found to be associated with more extensive DVTs of larger veins
      2. Arsov (2006) Croat Med 47(3): 433-9 [PubMed]
  2. Deep Vein Thrombosis
  3. Pulmonary Embolism
  4. Myocardial Infarction

VI. Management

  1. See Thrombophilia
  2. See Venous Thromboembolism
  3. See Anticoagulation in Thromboembolism

VII. References

  1. Jean-Louis and Sethuraman (2023) Crit Dec Emerg Med 37(7): 4-11

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