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Factor V Leiden

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What is Factor V Leiden

Factor V is one of many proteins involved in the sequence of reactions required for blood clotting to occur. The presence of Factor V promotes the clotting tendency of blood. Normally, the level of factor V in the blood is controlled by a substance called ‘activated protein C’. This protein breaks down factor V.

In patients with Factor V Leiden, an abnormality of their factor V gene means that activated protein C is unable to break down their factor V. The persistance of factor V in the bloodstream leads to a tendancy for blood clots to occur.


Statistics on Factor V Leiden

Factor V Leiden is found in 3-5% of healthy individuals in the West, and in 20% of patients with venous thrombosis (clots in the veins).


Risk Factors for Factor V Leiden

As Factor V Leiden is a disease based on a genetic abnormality, the most important predisposing factor is a family history of the disease.


Progression of Factor V Leiden

The disease is present from birth. However, patients are often affected later in life (young adult-middle age), if at all.


How is Factor V Leiden Diagnosed?

Pro-coagulation conditions such as Factor V Leiden can be treated by prophylactic anticoagulation therapy. This is usually only undertaken if the patient has suffered previous thrombosis, or if they are at high risk of thrombosis. Anticoagulation therapy is usually in the form of warfarin tablets. Warfarin therapy involves risks of increased bleeding, and the blood must be monitored regularly. Warfarin is not recommended during pregnancy. Pregnant women may not have any anticoagulation therapy, or may be given heparin injections instead.


Prognosis of Factor V Leiden

A proportion of the population with Factor V Leiden will suffer venous thrombosis. Thomboembolism, including pulmonary embolism, carries significant morbidity and mortality.


How is Factor V Leiden Treated?

Pro-coagulation (blood clotting) conditions such as Factor V Leiden can be treated by prophylactic anticoagulation (blood thinning) therapy. This is usually only undertaken if the patient has suffered previous thrombosis, or if they are at high risk of thrombosis. Anticoagulation therapy is usually in the form of warfarin tablets. Warfarin therapy involves risks of increased bleeding, and the blood must be monitored regularly. Warfarin is not recommended during pregnancy. Pregnant women may not have any anticoagulation therapy, or may be given heparin injections instead.


Factor V Leiden References

[1] Kumar P, Clark M. Clinical Medicine. Fourth Ed. WB Saunders, 1998. pp 409 – 410

Dates

Posted On: 2 July, 2003
Modified On: 6 February, 2008

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