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Factor V Leiden Thrombophilia

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What is Factor V Leiden Thrombophilia?

Factor V Leiden thrombophilia is an inherited disease which increases the chances of developing potentially dangerous blood clots. These blood clots tend to develop in the veins of the leg (deep vein thrombosis), but other types of blood clots are also possible.

Please note that most people who have the disease do not get abnormal blood clots. In the general population, 1 in 1,000 people develop a blood clot each year. In people with one mutation for factor V Leiden thrombophilia (and one normal copy of the gene, making them a carrier), that risk increases to between 4 and 8 in 1,000. This is comparable to the 3 to 6 fold increased risk of blood clots when taking an estrogen-containing birth control pill, which every obstetrician is already required to inform women about prior to taking the pill. In people with two mutations causing factor V Leiden thrombophilia, the risk increases substantially to between 18 and 80 in 1,000.

Certain factors increase the risk of blood clots in people with factor V Leiden thrombophilia. These can include smoking, advanced age, obesity, oral contraceptives, hormone replacement therapy, air travel, pregnancy, organ transplantation, surgery, cancer, and the presence of other genetic blood clotting disorders. Children with factor V Leiden thrombophilia rarely develop abnormal blood clots. Typically if these abnormal clots occur, they first appear in adulthood.

Pregnant women who have two genetic mutations that cause factor V Leiden thrombophilia are at an increased risk for certain complications including miscarriage, high blood pressure (preeclampsia), delayed physical development of the fetus, and a separation of the placenta from the uterine wall. Their risk of losing a pregnancy is 2 to 3 times greater than the general population. Please note however that most women with the disease will have normal pregnancies.

How common is Factor V Leiden Thrombophilia?

Roughly 1 in 5,000 people in the U.S. and Europe have two copies of the mutation that causes factor V Leiden thrombophilia, putting them at higher risk for abnormal blood clots.

Having one copy of the mutation that causes factor V Leiden thrombophilia (and one normal copy of the gene) is fairly common in the United States and Europe. Between 3 and 8% of Caucasians have one copy of the mutation. (Please note that this causes only a slightly elevated risk for abnormal clots.)

How is Factor V Leiden Thrombophilia treated?

A physician with knowledge of a person's overall health can help guide him or her in finding the appropriate treatment for factor V Leiden thrombophilia. For people with recurrent abnormal clots, long-term use of preventive medication may be recommended. For people with two factor V Leiden thrombophilia mutations who do not have a history of clotting, long-term use of medication may be recommended, although it may lead to a higher risk for excessive bleeding.

People with only one copy of the factor V Leiden thrombophilia mutation (and one normal gene) typically do not use any preventive medications, as the risks for excessive bleeding are seen to outweigh the anti-clotting benefits. During short periods of higher risk, such as surgery, trauma, or pregnancy, medication may be prescribed.

When clots are discovered, they are often treated with medication according to normal medical protocols. Women with deep vein thrombosis may be asked to wear compression stockings for a period of time following the clot.

People with factor V Leiden thrombophilia may want to avoid smoking, oral contraceptives, hormone replacement therapy, and obesity.

What is the prognosis for a person with Factor V Leiden Thrombophilia?

People with two mutations for factor V Leiden thrombophilia are at an 18 to 80 times greater risk than the general population for life-threatening blood clots. That said, the majority of people with the condition do not experience life-threatening blood clots and will live normal lifespans.

Studies have shown that people with only one mutation for factor V Leiden thrombophilia have a normal lifespan.


Genetics Home Reference

Explanations of an extensive number of genetic diseases written for everyday people by the U.S. government's National Institutes of Health.

The National Alliance for Thrombosis and Thrombophilia

A patient-led advocacy organization providing patient education and professional training on the signs, symptoms and prevention of blood clots and clotting disorders.

120 White Plains Road, Suite 100
Tarrytown, NY 10591
Phone: (914) 220-5040
Secondary Phone: (877) 4NO-CLOT

Thrombophilia Awareness Project

A website founded by Deborah Okner Smith, a woman with factor V Leiden thrombophilia, the site offers stories shared by other people living with the disease as well as a Q&A with a physician about various aspects of the disease.

Other names for Factor V Leiden Thrombophilia

  • Leiden Type APC Resistance
  • Factor V Deficiency
  • Hereditary Resistance to Activated Protein C
  • Labile Factor Deficiency
  • Factor V Leiden Thrombophilia
  • Owren Parahemophilia
  • Parahemophilia
  • Factor V Leiden Mutation

Counsyl has renamed its products effective July 19, 2017. The Family Prep Screen is now the Foresight Carrier Screen.

The new names now appear on all communications from Counsyl. If you have any questions, please contact Counsyl directly.

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