F5 and Patent foramen ovale: However, recently factor V Leiden and prothrombin G20210A mutations have been described as being significantly more prevalent in patients with cryptogenic stroke and PFO than in matched healthy controls (11% versus 2%; 95% CI, 0.04 to 0.94; p<0.05) or cryptogenic stroke without PFO (11% versus 1.1%; 95% CI, 1.09 to 109; P<0.05) [46].