Factor V Leiden

Last revised by Craig Hacking on 14 Mar 2023

Factor V Leiden is a primary hypercoagulable state due to a variant (mutated form) of human factor V (five). Factor V is one of several coagulation factors that assist in the clotting pathway.

Heterozygous factor V Leiden may be present in around 5% of the European population and is most common in people of Northern European descent and in some Middle Eastern populations. The homozygous and more severe form is found in fewer than 1%.

Patients can have multiple thromboembolic complications which include 1,3,4:

Interestingly, the risk of pulmonary embolism may be lower than the risk of deep venous thrombosis in patients with factor V Leiden, known as the 'factor V Leiden paradox' 4.

Factor V Leiden is caused by a single point mutation in the F5 gene, located on chromosome 1 1,4. Factor V Leiden has a poor anticoagulant response to activated protein C, which normally degrades activated factor V, resulting in a prothrombotic state 4.

There are no specific radiographic features. Imaging findings are mainly in the form of identifying thromboembolic complications.

The presence of factor V Leiden does not change anticoagulant management in patients with thromboembolism, and there is currently no role for prophylactic anticoagulation for patients who are homozygous or heterozygous to the factor V Leiden allele 1.

The mutated factor is named after the city of Leiden in the Netherlands, where the seminal research to discover its causative genetic mutation was conducted in 1994, by Rogier M Bertina​ and his Dutch colleagues 5.

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