Factor V Leiden: Mutation, Symptoms and Treatment
Factor V Leiden is a genetic mutation that increases the risk of blood clots. It is the most common hereditary cause of excessive blood clotting (thrombophilia).
Things worth knowing about "Leiden factor 5"
Factor V Leiden is a genetic mutation that increases the risk of blood clots. It is the most common hereditary cause of excessive blood clotting (thrombophilia).
What is Factor V Leiden?
Factor V Leiden (also referred to as the Factor 5 Leiden mutation) is a genetic variant of coagulation factor V that leads to an increased tendency to form blood clots, a condition known as thrombophilia. It is the most common inherited thrombophilia in populations of European descent, affecting approximately 3–8 % of people in Central and Northern Europe.
Causes and Genetics
The mutation is caused by a single point change in the F5 gene on chromosome 1, where the amino acid arginine at position 506 is replaced by glutamine (R506Q). As a result, the clotting protein Factor V can no longer be properly inactivated by the natural anticoagulant enzyme Activated Protein C (APC) – a condition called APC resistance.
- Heterozygous carriers: One mutated copy of the gene (inherited from one parent) – the risk of thrombosis is increased 4–8 times.
- Homozygous carriers: Two mutated copies (inherited from both parents) – the risk of thrombosis is increased 50–80 times.
Symptoms and Complications
Many people with Factor V Leiden never experience symptoms. However, when a blood clot does form, the following may occur:
- Deep vein thrombosis (DVT): Swelling, pain, redness, and warmth, most often in the leg
- Pulmonary embolism: Sudden shortness of breath, chest pain, coughing, or rapid heartbeat (medical emergency)
- Thrombosis in unusual locations: Such as in liver, spleen, or brain veins
- Pregnancy complications: Increased risk of miscarriage, pre-eclampsia, or placental insufficiency
Diagnosis
Diagnosis is established through laboratory testing:
- APC resistance test: A functional coagulation test that measures how the blood responds to activated protein C. In Factor V Leiden, the inhibitory effect is reduced.
- Genetic testing (DNA analysis): Confirms the specific mutation in the F5 gene and distinguishes between heterozygous and homozygous carrier status.
- Testing is recommended for individuals with an unexplained first thrombosis, a positive family history, or thrombosis during pregnancy.
Treatment and Management
Not all carriers of the Factor V Leiden mutation require treatment. Therapy is tailored to the individual risk profile:
Medical Treatment
- Anticoagulants (blood thinners): For acute thrombosis, heparin or direct oral anticoagulants (DOACs) such as rivaroxaban or apixaban are used.
- Long-term anticoagulation: Individuals with recurrent thrombosis or very high risk may require ongoing treatment.
Preventive Measures
- Avoiding additional risk factors such as smoking, obesity, and prolonged immobility
- Thrombosis prophylaxis during surgery or long-haul flights
- Special monitoring and anticoagulation during pregnancy if indicated
- Caution with hormonal contraceptives (the pill), which can further increase clotting risk
References
- Rosendaal FR, Koster T, Vandenbroucke JP, Reitsma PH. High risk of thrombosis in patients homozygous for factor V Leiden (activated protein C resistance). Blood. 1995;85(6):1504–1508.
- World Health Organization (WHO). Thrombosis and Haemostasis. WHO Technical Report Series. Geneva, 2023.
- Middeldorp S. Factor V Leiden and the risk of venous thromboembolism. Hematology Am Soc Hematol Educ Program. 2011;2011:301–306.
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