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Insight

Aug 11, 2025, 04:34

Factor V Leiden: Quick Facts

Dr. Chokri Ben Lamine, Adult Hematology and Stem Cell Transplantation Assistant Consultant at Oncology Center of Excellence at King Faisal Specialist Hospital & Research Center, shared a post on, recently shared on X:

“Factor V Leiden – Hematology Thread
Most common inherited thrombophilia
Everything you need: pathophysiology, risks, management, MCQ, OSCE

What is Factor V Leiden?

Mutation in F5 gene (Arg506Gln) → resistance to activated protein C (APC)
Results in prolonged clotting activity → high risk of venous thromboembolism (VTE)

Prevalence

3–8% in Caucasians
Heterozygous: ~7x higher VTE risk
Homozygous: ~20–80x higher VTE risk
Rare in Asians, Africans

When to Suspect

Unprovoked VTE <50 yrs
Recurrent VTE
VTE in unusual sites (e.g., cerebral, mesenteric veins)
Strong family hx of clots
Neonatal purpura fulminans (if compound with protein C deficiency)
OCP or pregnancy-related clots

Testing

Start with APC resistance assay
Confirm with DNA test for F5 mutation
Only test if results will change management (per ASH)

Management – Acute VTE

Anticoagulate as per standard (DOACs, warfarin, LMWH)
Duration: depends on risk of recurrence
No need to treat asymptomatic heterozygotes

Pregnancy

Heterozygous, no VTE history: no routine anticoagulation
Heterozygous + VTE history: LMWH throughout pregnancy + 6 weeks postpartum
Homozygous or compound mutation: prophylaxis recommended

Avoid

Estrogen-based OCPs
Smoking
Prolonged immobility without prophylaxis

Exam Pearls

Most common inherited thrombophilia
higher DVT > PE
DOACs preferred unless contraindicated
Routine screening not recommended
Counsel before OCPs, pregnancy, surgery

30 year old female with 1st unprovoked DVT, heterozygous FVL, no other RFs. Completed 6 mo anticoagulation. What next?
Stop anticoagulation; counsel on OCP risks and recurrence prevention

OSCE Scenario 1

Young woman with VTE on OCP
Take history
Order FVL test if family history
Counsel on stopping estrogen, using progestin-only methods

OSCE Scenario 2

Pregnant FVL heterozygote, no prior VTE
Explain that prophylaxis is not needed unless additional risks
Plan close monitoring, early postpartum prophylaxis if needed

OSCE Scenario 3

Homozygous FVL patient needing surgery
Plan perioperative LMWH
Counsel on risk, early ambulation, compression devices

Landmark References (Aug 2025)

1.NCCN 2025 – Thrombophilia & VTE risk stratification
2.ASH 2023 – Management guidelines on inherited thrombophilia
3.GeneReviews – Factor V Leiden update July 2024
4.BMJ 2022 – Risk of VTE recurrence in FVL
5.Front Cardiovasc Med 2022 – Meta-analysis on FVL and VTE recurrence.”

Stay updated on the latest with Hemostasis Today.

APC APC Resistance Assay ASH BMJ Chokri Ben Lamine Front Cardiovasc Med FVLeiden GeneReviews Health Hematology Hemostasis Today Medicine NCCN 2025 Neonatal Purpura Fulminans Perioperative anticoagulation Pregnancy Recurrent VTE Thrombophilia Unprovoked VTE

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