What Are the Implications of Having Factor V Leiden?
Heterozygous factor V Leiden is found in about 5% of the white population and is most common in people of Northern European descent and in some Middle Eastern populations, whereas the homozygous form is found in fewer than 1%. Factor V Leiden is less common in the Hispanic populations and is rare in Asian, African, and Native American populations. Factor V Leiden is associated with an increased risk of developing an episode of DVT (with or without a PE). Approximately 1 in every 1000 people will develop a DVT or PE each year, and this increases from about 1 in 10 000 for those in their twenties to about 5 in 1000 for those in their seventies. Heterozygous factor V Leiden increases the risk of developing a first DVT by 5- to 7-fold (or 5 to 7 in 1000 people each year). Thus, even though the relative risk of developing a DVT seems high, the absolute risk of having a DVT is still quite low with factor V Leiden. Factor V Leiden is thus a weak risk factor for developing blood clots; in fact
