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?
We all inherit two copies of the F5 (factor V) gene. We inherit one copy from our mother and the other from our father. As a result, our risk for having factor V Leiden thrombophilia depends on the genetic status of each of our parents.
Most people with factor V Leiden thrombophilia have one "normal" F5 gene and one with the factor V Leiden gene mutation. People with one copy of the mutation are called heterozygotes. Assuming this person and a person without the mutation have a child, this couple would have a 50%, or 1 in 2 chance of having a child with a single F5 mutation.
Factor V Leiden thrombophilia is a relatively common condition. In some families, both parents have the F5 mutation. In this scenario, each child of the couple would have a 25% or 1 in 4 chance of having two mutations, a 25% chance of having no mutation, and a 50% chance of having a one mutation.
People with two copies of the F5 mutation are said to be "homozygotes." They will always pass one copy of the mutated gene to their children. A child's risk for a second mutation will depend on whether or not his or her other parent has the F5 mutation.
Last updated: 1/24/2017
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
We hope this information is helpful. We strongly recommend you discuss this information with your doctor. If you still have questions, please