How do people inherit factor V Leiden thrombophilia?
The chance of developing an abnormal blood clot depends on whether a person has one or two copies of the factor V Leiden mutation in each cell. People who inherit two copies of the mutation, one from each parent, have a higher risk of developing a clot than people who inherit one copy of the mutation. Considering that about 1 in 1,000 people per year in the general population will develop an abnormal blood clot, the presence of one copy of the factor V Leiden mutation increases that risk to 3 to 8 in 1,000, and having two copies of the mutation may raise the risk to as high as 80 in 1,000.
