Factor V Leiden

[3][4][5] It is named after the Dutch city of Leiden, where it was first identified in 1994 by Rogier Maria Bertina under the direction of (and in the laboratory of) Pieter Hendrik Reitsma.

[6] Despite the increased risk of venous thromboembolisms, people with one copy of this gene have not been found to have shorter lives than the general population.

[citation needed] Symptoms of factor V Leiden include:[citation needed] The use of hormones, such as oral contraceptive pills (OCPs) and hormone replacement therapy (HRT), including estrogen and estrogen-like drugs taken after menopause, increases the risk of developing DVT and PE.

Women with heterozygous factor V Leiden who are making decisions about OCP or HRT use should take these statistics into consideration when weighing the risks and benefits of treatment.

[12] Suspicion of factor V Leiden being the cause for any thrombotic event should be considered in any Caucasian patient below the age of 45, or in any person with a family history of venous thrombosis.

[13] In addition, temporary treatment with an anticoagulant such as heparin may be required during periods of particularly high risk of thrombosis, such as major surgery.

[16][17] One study also suggested "that the factor V‐Leiden mutation segregates in populations with significant Caucasian admixture and is rare in genetically distant non‐European groups.

The risk of developing a clot in a blood vessel depends on whether a person inherits one or two copies of the factor V Leiden mutation.

Inheriting one copy of the mutation from a parent (heterozygous) increases by fourfold to eightfold the chance of developing a clot.

People who inherit two copies of the mutation (homozygous), one from each parent, may have up to 80 times the usual risk of developing this type of blood clot.

While only 1 percent of people with factor V Leiden have two copies of the defective gene, these homozygous individuals have a more severe clinical condition.

[citation needed] Women with factor V Leiden have a substantially increased risk of clotting in pregnancy (and on estrogen-containing birth control pills or hormone replacement) in the form of deep vein thrombosis and pulmonary embolism.