Factor V Leiden

Last revised by Daniel J Bell on 14 Sep 2021

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, 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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Cases and figures

  • Case 1: with pulmonary embolism
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  • Case 2: with cortical vein thrombosis
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