What is Factor V Leiden (Factor 5 Leiden)?

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Last updated: April 28, 2025View editorial policy

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From the Guidelines

Factor 5 Leiden is a genetic mutation that increases the risk of blood clotting, particularly deep vein thrombosis and pulmonary embolism, and is associated with a higher risk of recurrent venous thromboembolism, especially in individuals with persistent risk factors or idiopathic venous thromboembolism 1.

Definition and Mechanism

Factor 5 Leiden is a mutation that affects Factor V, a protein involved in the blood clotting process, making it resistant to activated protein C, a natural anticoagulant that regulates clotting 1. This leads to an increased risk of developing dangerous blood clots, particularly in the legs or lungs.

Inheritance and Risk

The mutation is inherited, and individuals can have either one copy (heterozygous) or two copies (homozygous) of the mutation, with the latter causing a higher risk of clotting problems 1. The lifetime risk for venous thrombosis in factor V Leiden heterozygotes is approximately 10%, and for homozygotes, it is greater than 80% 1.

Management and Prevention

Management typically involves awareness of risk factors, possible preventive blood thinners during high-risk periods, such as pregnancy, hormone therapy, surgery, or long periods of immobility, and prompt treatment if clots develop 1. Testing for factor V Leiden is recommended for individuals with recurrent venous thromboembolism, especially those with persistent risk factors or idiopathic venous thromboembolism, as it may influence patient management and guide antithrombotic prophylaxis 1.

Key Points

  • Factor 5 Leiden increases the risk of blood clotting, particularly deep vein thrombosis and pulmonary embolism
  • The mutation is inherited and can be heterozygous or homozygous
  • Management involves awareness of risk factors, preventive blood thinners, and prompt treatment if clots develop
  • Testing for factor V Leiden is recommended for individuals with recurrent venous thromboembolism, especially those with persistent risk factors or idiopathic venous thromboembolism 1

From the Research

Definition of Factor V Leiden

  • Factor V Leiden is a mutation in the factor V gene that increases the risk of blood clots [ 2 ]
  • It is a genetic disorder that affects the blood's ability to clot, leading to an increased risk of thrombosis [ 2 ]

Relationship with Pregnancy Complications

  • Factor V Leiden mutation has been linked to recurrent pregnancy loss (RPL) and other pregnancy complications [ 2 ]
  • Studies have investigated the use of low molecular weight heparin (LMWH) and aspirin to prevent pregnancy complications in women with factor V Leiden mutation [ 2 ]

Clinical Significance

  • Factor V Leiden mutation can increase the risk of blood clots and pregnancy complications, making it an important consideration in clinical practice [ 2 ]
  • The use of LMWH and aspirin may help prevent pregnancy complications in women with factor V Leiden mutation, although more research is needed to confirm this [ 2 ]

Diagnosis and Treatment

  • Diagnosis of factor V Leiden mutation typically involves genetic testing [ 2 ]
  • Treatment may involve the use of anticoagulant medications, such as LMWH and aspirin, to prevent blood clots and pregnancy complications [ 2 ]

References

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Research

Aspirin, low molecular weight heparin, or both in preventing pregnancy complications in women with recurrent pregnancy loss and factor V Leiden mutation.

The journal of maternal-fetal & neonatal medicine : the official journal of the European Association of Perinatal Medicine, the Federation of Asia and Oceania Perinatal Societies, the International Society of Perinatal Obstetricians, 2020

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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