Factor V Leiden

Key points

• Factor V Leiden (activated protein C resistance) is the most common inherited thrombophilia, present in around 5% of the UK population
• It is due to a gain-of-function mutation in the Factor V gene
• The mutation makes Factor Va resistant to cleavage by activated protein C, resulting in a prothrombotic state
• Heterozygotes have a moderately increased risk of venous thromboembolism; homozygotes carry a much higher risk