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Nature of the Genetic Difficulty

Factor V Leiden Throbophilia occurs when there is a genetic mutation that occurs in the gene that codes for thrombophilia, which is the increased probability of a person to form abnormally large blood clots.
This creates a greater risk for a pulmonary embolism or deep venous thrombosis. The mutation occurs in the Factor V gene (F5) which codes for a blood clotting protien, however in the case of Factor V Leiden Thrombosis, the activated protein C (which deactivates Factor V) does not function properly and so allows the blood clotting process to continue longer. This increases the risk of abnormal blood clots.

Basic Facts of Disease

1.It is the most common inherited form of a hypercoagulating disorder in Caucasians.
2. 3-8% of the Caucasian populations in the U.S and Europe have one copy of the gene.
3. 1 in 50,000 has two copies
4. Having one copy of the Factor V gene increases your odds of having an abnormal blood clot to 1 in 125 to 1 in 250.
5. Having two copies increases that risk to 1 in 12
6. Oral contraceptives and estrogen therapy may increase the risk of a mutation in the F5 gene.

Other Names:
-Leiden Type APC Resistance
-Factor V Deficiency
-Hereditary Resistance to Activated Protein C
-Labile Factor Deficiency
-Factor V Leiden Thrombophilia
-Owren Parahemophilia
-Factor V Leiden Mutation

-Having a first Deep Venous Thrombosis (DVT) or Pulmonary Embolism (PE) before 50 years of age.
-Having recurring DVT or PE.
-Having venous thrombosis in unusual sites in the body such as the brain or the liver.
-Having a DVT or PE during or right after pregnancy.
-Having a history of unexplained pregnancy loss in the second or third trimester.
-Having a DVT or PE and a strong family history of venous thromboembolism.


The majority of people with Factor v Leiden Thrombophilia do not experience abnormal blood clots and live normal lifespans.

Sources Cited