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Leiden Mutation

The Factor V Leiden mutation, a common inherited genetic condition, causes Factor V resistance to Protein C, increasing the risk of abnormal blood clots, especially in the legs and lungs.

Hematology
Factor V Leiden mutation is a genetic disorder that increases a person's risk of developing abnormal blood clots, most commonly in the legs (deep vein thrombosis - DVT) or lungs (pulmonary embolism - PE). It is the most common inherited cause of thrombophilia, which is a condition that increases the tendency to form blood clots. The mutation affects Factor V, a protein in the blood clotting cascade. Normally, Factor V is inactivated by Protein C, an anticoagulant protein, to prevent excessive clotting. However, in individuals with the Factor V Leiden mutation, Factor V is resistant to inactivation by Protein C, leading to a prolonged pro-clotting state. While many individuals with the mutation never develop clots, the risk significantly increases when combined with other risk factors. Causes: Factor V Leiden mutation is a genetic condition, meaning it is inherited from one or both parents. It involves a specific change in the gene that produces Factor V, a protein involved in blood clotting.
  • Genetic Mutation:
    • The mutation is a single point mutation (a change in one building block of DNA) in the F5 gene, located on chromosome 1.
    • This specific mutation changes an amino acid in the Factor V protein, making it resistant to inactivation by activated Protein C (APC). APC is a natural anticoagulant that helps slow down clotting.
  • Inheritance Pattern:
    • Autosomal Dominant: You only need to inherit one copy of the mutated gene from one parent to have Factor V Leiden.
    • Heterozygous: Inheriting one copy of the mutated gene (from one parent). This is the most common form and carries a moderately increased risk of clotting (3-8 times the normal risk).
    • Homozygous: Inheriting two copies of the mutated gene (one from each parent). This is rarer but carries a significantly higher risk of clotting (up to 80 times the normal risk) and often leads to earlier and more severe clotting events.
  • Increased Risk of Clotting: The mutation itself does not guarantee a clot, but it significantly increases the risk, especially when combined with other factors.
Symptoms: Factor V Leiden mutation itself does not cause symptoms. Symptoms only appear if and when a blood clot develops. The symptoms will depend on where the blood clot forms.
  • Symptoms of Deep Vein Thrombosis (DVT):
    • Pain or tenderness in the affected limb (most commonly leg or thigh).
    • Swelling of the affected limb.
    • Redness or discoloration of the skin.
    • Warmth in the affected area.
    • Often, a heavy or aching sensation in the leg.
  • Symptoms of Pulmonary Embolism (PE):
    • Sudden shortness of breath.
    • Chest pain (often sharp, worse with deep breath).
    • Rapid heart rate.
    • Coughing (may include bloody mucus).
    • Dizziness or lightheadedness.
    • Sweating.
    • Anxiety.
    • These are life-threatening symptoms and require immediate medical attention.
  • Other Less Common Clotting Events:
    • Cerebral Vein Thrombosis: Blood clot in the veins of the brain, causing severe headache, seizures, or neurological deficits.
    • Mesenteric Ischemia: Blood clot in the arteries or veins supplying the intestines, causing severe abdominal pain.
    • Recurrent Miscarriages: Increased risk of recurrent pregnancy loss due to blood clots in the placenta.
Diagnosis: Diagnosis of Factor V Leiden mutation involves a blood test to detect the specific genetic mutation. This test is typically performed when there is a personal or family history of unexplained blood clots.
  • Medical History: The doctor will inquire about any personal history of blood clots (DVT, PE, stroke, heart attack) and any family history of clotting disorders.
  • Blood Tests:
    • Activated Protein C (APC) Resistance Test: This initial screening test checks how well Factor V responds to inactivation by Protein C. If it's resistant, it suggests Factor V Leiden.
    • Genetic Test for F5 Gene Mutation: If the APC resistance test is abnormal, a specific DNA test confirms the presence of the Factor V Leiden mutation. This test can determine if a person is heterozygous (one copy) or homozygous (two copies) for the mutation.
  • Imaging Tests (if a clot is suspected):
    • Duplex Ultrasound: For diagnosing DVT in the legs.
    • CT Pulmonary Angiogram (CTPA): For diagnosing PE in the lungs.
Treatment: Treatment for Factor V Leiden mutation focuses on preventing blood clots and managing existing clots. Not everyone with the mutation requires lifelong anticoagulant therapy, as the treatment strategy depends on individual risk factors and history of clotting events.
  • For Individuals with a History of Blood Clots:
    • Anticoagulant Medications (Blood Thinners):
      • Warfarin (Coumadin): A common treatment that reduces the ability of blood to clot. Requires regular blood tests (INR) to monitor.
      • Direct Oral Anticoagulants (DOACs): (e.g., rivaroxaban, apixaban, dabigatran, edoxaban) Newer blood thinners that do not require frequent monitoring. Often used for treating acute clots and preventing recurrence.
    • The duration of anticoagulant therapy depends on the individual's clot history, type of clot, and other risk factors. It may be short-term (e.g., 3-6 months) or lifelong.
  • For Asymptomatic Individuals with Factor V Leiden (No History of Clots):
    • Lifelong blood thinners are generally *not* recommended as a primary prevention strategy due to bleeding risks.
    • Risk Factor Management: Focus on avoiding or mitigating other clotting risk factors.
    • Prophylaxis in High-Risk Situations: Anticoagulants may be temporarily used during periods of increased risk, such as:
      • Surgery or prolonged immobility.
      • Long-haul flights (discuss with doctor).
      • Pregnancy and postpartum period (heparin injections often used).
      • Use of estrogen-containing birth control pills or hormone replacement therapy (often advised against due to significantly increased clot risk).
  • For Pregnant Women with Factor V Leiden:
    • Often prescribed low molecular weight heparin (LMWH) injections during pregnancy and postpartum to prevent clots, especially if there's a history of clots or pregnancy loss.
  • Lifestyle Modifications:
    • Maintain a healthy weight.
    • Regular exercise.
    • Avoid prolonged immobility (e.g., get up and move during long flights/car rides).
    • Quit smoking.
    • Stay hydrated.
Management of Factor V Leiden mutation requires careful consideration of individual risk factors and a close relationship with a healthcare provider, often a hematologist, to determine the most appropriate prevention and treatment strategies.

Related Medications

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