Notably, the factor V Leiden mutation [26], which is a common risk factor for thrombophilia, is a known variant of F5 that is a member of the complement and coagulation cascades like CR1. Although, we did not find the factor V Leiden mutation, the F5 gene accumulated the most new non-synonymous homozygous variants in both children. This evidence concerns the gene F5 and Rare hereditary thrombophilia.