Factor V Leiden

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.

Epidemiology

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%.

Associations

• Behçet disease ²

Clinical presentation

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

• emboli

  • pulmonary embolism

• venous thromboses

  • deep venous thrombosis

  • superficial thrombophlebitis

  • dural venous sinus thrombosis

  • portal vein thrombosis

• organ infarctions

  • splenic infarction

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.

Pathology

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.

Radiographic features

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

Treatment and prognosis

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

History and etymology

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.