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In the last 2 posts, we discussed the pathophysiology and initial management of venous thromboembolism. As a hematologist, I see many consults for consideration of hypercoagulable work-up for patients that have had a VTE episode.
In the upcoming posts, I’d like to do a deeper dive into the various hypercoagulable conditions that affect humans.
Let’s start with Factor V Leiden
What is Factor V?
Factor V is a clotting factor. It is produced by the liver and it helps stabilize the fibrin clot which forms when there is vessel wall injury.
What is factor V Leiden?
Factor V Leiden is a variant of factor V in which a point mutation in the gene coding for factor V renders the factor more resistant to degradation by activated protein C. It can manifest as homozygous or heterozygous states. This is also known as activated protein C resistance. The name “Leiden” comes from the Dutch city in which this variant was discovered
If you don’t have access to factor V leiden testing, check if the lab can run an activated protein C resistance test which can provide a clue for presence/absence of factor V Leiden.
Prevalence:
5% of Caucasian population can have Heterozygous Factor V Leiden
Homozygous is found in <1% population
Less common in the Hispanic population and rare in the Asian, african and native american populations.
Risk of VTE:
Heterozygous factor V Leiden increases the risk of developing a DVT by 5 to 7 fold each year (or 5-7 in 1000 people each year).
Homozygous factor V Leiden increases the risk of developing VTE by 25-50 fold- so much greater than homozygous states
More often than not, there is another risk factor present in patients with factor V Leiden who develop blood clots such as estrogen exposure, testosterone exposure, long flights/drives, cancer, surgery.
Having factor V leiden does not increase the risk of heart attacks and strokes
Management:
1st Acute VTE episode: same as initial provoked/unprovoked VTE
Recurrent provoked VTE: consider long-term AC
Recurrent unprovoked VTE: likely benefit from long-term AC
Pregnancy: close monitoring unless patient has personal history of venous thromboembolism
Overall, the risk of developing VTE with factor V Leiden is not considered very high to warrant prophylactic anticoagulation
Reference: ASH SAP 8th edition, Ornstein et al, Circulation 2003
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