Blood Clotting Disorder Hypercoagulation Factor V Leiden

Factor V Leiden is a genetic disorder that causes a person’s blood to clot abnormally. Specifically, people with Factor V Leiden are at an increased risk of developing blood clots. Affecting approximately 5 percent of Caucasians and 1.2 percent of African Americans, Factor V Leiden is the most common hereditary blood disorder in the United States.

Factor V Leiden is a serious condition that can be life threatening. However, the majority of the people who are diagnosed with the disorder never experience symptoms of abnormal blood clotting and live normal lives.

Factor V Leiden Fact

Factor V Leiden is a disorder, not a disease.

Factor V Leiden Causes

Factor V Leiden is a genetic disorder that is caused by a mutation in the F5 gene. The F5 gene stimulates chemical reactions within the body that stimulate the clotting of blood after an injury.

In a person who doesn’t have Factor V Leiden, the F5 gene is eventually shut down by a protein to keep the blood clots from getting too big. For those with Factor V Leiden, however, the protein has no effect. This can result in abnormal clotting.

Causes of Blood Clots

Although individuals who are born with the Factor V Leiden genetic mutation are at an increased risk of developing blood clots, other factors can contribute to blood clots, including:

  • obesity
  • pregnancy
  • sedentary lifestyle
  • smoking
  • taking oral contraceptives.

Factor V Leiden Types

There are two copies of the F5 gene. Thus, there are two types of Factor V Leiden, heterozygous and homozygous:

  • People with heterozygous Factor V Leiden have inherited only one copy of the mutated F5 gene.
  • People with homozygous Factor V Leiden inherited both copies of the mutated gene.

Heterozygous Factor V Leiden is the most common form of the disorder. In order for a person to have homozygous Factor V Leiden, he must inherit a mutated gene from both parents.

The homozygous form is more serious than the heterozygous form. People who have homozygous Factor V Leiden have a higher chance of experiencing abnormal clotting and of developing deep vein thrombosis, which are blood clots in the deep veins.

Diagnosis and Treatment for Factor V Leiden

A blood test can determine if you carry the genetic mutation for Factor V Leiden. However, since the presence of the genetic mutation alone will not necessarily cause blood clots, doctors do not normally test for Factor V Leiden.

However, doctors will usually test for the disorder under the following circumstances:

  • if you’ve developed a blood clot
  • if you experience pulmonary embolism (a blood clot in the lung)
  • if you have a stroke
  • if you go into convulsions during pregnancy
  • if you have a miscarriage.

Treatment usually includes lifestyle changes and taking anti-coagulant drugs. The most common drug prescribed to those with Factor V Leiden is warfarin (brand name Coumadin®).

However, some physicians worry that prescribing warfarin, which thins the blood, might actually put patients at greater risk, as blood-thinning medications can cause internal bleeding. If you have Factor V Leiden, talk to your doctor about the best treatment options for you.


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Mesa, Ruben (2006). Factor V Leiden: Are There Different Types? Retrieved September 21, 2007, from the Mayo Clinic Web site:

Paterson, S. (March 7, 2007).DVT victim’s family wants babies tested for the ‘killer’ gene; Around 5 percent of the population could be at risk of clotting. The Herald (Glasgow). p.7.