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Factor V Leiden

Factor V Leiden is a topic covered in the 5-Minute Clinical Consult.

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  • Factor V Leiden is a genetic mutation at the activated protein C (APC) cleavage site on the factor V and Va molecule leading to the most common form of inherited thrombophilia.
  • System(s) affected: cardiovascular, gastrointestinal, hemo-/lymphatic/immunologic, nervous, pulmonary, reproductive
  • Synonym(s): factor V Leiden thrombophilia; factor V Leiden mutation, hereditary APC resistance

Pediatric Considerations
Potential for increased thrombosis risk in patients with factor V Leiden and concomitant risks

Pregnancy Considerations
  • Recurrent pregnancy loss is a possible complication.
  • Increased thrombotic risk in pregnancy and postpartum (additive) especially in homozygous state
  • Possible increased risk of IUGR, preeclampsia, placental abruption, evidence mixed


Studies estimate ~5–8% occurrence of heterozygosity in Caucasians, Hispanic Americans ~2 %, African American ~1%, and Asian Americans ~0.45%.

Etiology and Pathophysiology

  • Factor V circulates in the plasma. When exposed to tissue factor, factor V amplifies the production of thrombin which further promotes clotting by activating factor V into procoagulant factor Va.
  • For balance, thrombin also promotes APC production which will cleave and inactivate factor V, Va, and VIII, thereby keeping the clotting cascade in check (negative feedback loop).
  • In factor V Leiden, a point mutation at the binding site of APC (Arg506Glu) renders it less able to cleave factor V or Va. This, in turn, reduces the anticoagulant role of factor V as a cofactor to APC and increases the procoagulant role of activated factor V, as there is now 20-fold slower degradation of factor Va.

Risk Factors

  • Risk for venous thromboembolism (VTE) is ~7-fold in heterozygous and ~80-fold in homozygous factor V Leiden individuals, compared with individuals without the mutation (1). This risk is compounded/increased by the presence of the following:
    • Having non-O blood type (A, B, or AB) (2- to 4-fold)
    • Oral contraceptives: homozygotes up to 100-fold; heterozygotes, 35-fold. The increased risk is halved when the patient uses desogestrel-containing oral contraceptives.
    • Hormone replacement therapy (HRT) and selective estrogen receptor modulators (SERMs) both increase the risk of thrombosis; in patients with factor V Leiden, that risk is compounded.
    • Pregnancy and homozygous factor V Leiden increase the risk of thrombosis 7- to 16-fold during pregnancy and the puerperium.
  • Data are conflicting with regard to risk for recurrent VTE for patients with factor V Leiden but trend toward an increased risk (2,3).

General Prevention

Patients with factor V Leiden without thrombosis do not require prophylactic anticoagulation.

Commonly Associated Conditions

Venous thrombosis

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Stephens, Mark B., et al., editors. "Factor V Leiden." 5-Minute Clinical Consult, 27th ed., Wolters Kluwer, 2019. Medicine Central, im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/116222/all/Factor_V_Leiden.
Factor V Leiden. In: Stephens MB, Golding J, Baldor RA, et al, eds. 5-Minute Clinical Consult. 27th ed. Wolters Kluwer; 2019. https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/116222/all/Factor_V_Leiden. Accessed April 24, 2019.
Factor V Leiden. (2019). In Stephens, M. B., Golding, J., Baldor, R. A., & Domino, F. J. (Eds.), 5-Minute Clinical Consult. Available from https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/116222/all/Factor_V_Leiden
Factor V Leiden [Internet]. In: Stephens MB, Golding J, Baldor RA, Domino FJ, editors. 5-Minute Clinical Consult. Wolters Kluwer; 2019. [cited 2019 April 24]. Available from: https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/116222/all/Factor_V_Leiden.
* Article titles in AMA citation format should be in sentence-case
TY - ELEC T1 - Factor V Leiden ID - 116222 ED - Stephens,Mark B, ED - Golding,Jeremy, ED - Baldor,Robert A, ED - Domino,Frank J, BT - 5-Minute Clinical Consult, Updating UR - https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/116222/all/Factor_V_Leiden PB - Wolters Kluwer ET - 27 DB - Medicine Central DP - Unbound Medicine ER -