Hereditary thrombophilia is responsible for most cases of predisposition to VTE and the greatest prevalence is of a resistance to activated protein C (Svensson and Dahlbäck, 1994), caused in most cases by a point mutation in the gene of the coagulation factor V (FV), known as Factor V Leiden (FVL), FV: R506Q or FV: G1691A. The gene discussed is F5; the disease is Rare hereditary thrombophilia.