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Genetic and Rare Diseases Information Center (GARD)

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Factor V Leiden thrombophilia


* Not a rare disease
Other Names for this Disease
  • APC resistance, Leiden type
  • Hereditary resistance to activated protein C
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Your Question

My husband has factor V Leiden. How could he have this when nobody else in his family has it including his parents? Is this disorder always passed down or can it skip a generation? What is the chance that our kids will have it?

Our Answer

We have identified the following information that we hope you find helpful. If you still have questions, please contact us.

How is factor V Leiden inherited?

Factor V Leiden is a genetic condition and can be inherited from a parent. It is important to understand that each person inherits two copies of every gene, one from their mother and the other copy from their father.  Individuals who inherit one copy of the factor V Leiden mutation from a parent are called heterozygotes. Heterozygotes have a 50% chance with each pregnancy of passing the mutated gene to their offspring (and therefore they also have a 50% chance of having a child who does not inherit the gene mutation). People who inherit two copies of the mutation, one from each parent, are called homozygotes. Homozygotes will always pass one copy of the mutated gene to their offspring.

If both parents are heterozygotes (carry one factor V Leiden mutation) than they would have a 25% chance of having a child with two factor V Leiden mutations, a 25% chance of having a child with no mutations, and a 50% chance of having a child with one mutation.

Last updated: 4/20/2011

Can someone without any family history of factor V Leiden still develop the condition?

Yes. There are a couple different scenarios that can explain why an individual with factor V Leiden thrombophilia may appear to be the first affected in their family. For example, it is possible that an individual’s parent(s) carried the factor V Leiden mutation, but never developed thrombophilia. While factor V Leiden mutations increase a person’s likelihood of developing a blood clot, not all individuals with the gene mutation develop them.  It is also possible that the gene mutation occurred randomly for the first time in either the mother’s egg or father’s sperm. Mutations that occur only in an egg or sperm cell, or those that occur just after fertilization (i.e., conception), are called new or de novo mutations. Click here to read more about gene mutations and how they can occur.
Last updated: 4/20/2011