In patients with homozygous FV Leiden or homozygous prothrombin G20210A mutation or with other hereditary thrombophilic states (such as deficiency of antithrombin III, protein C, or protein S), indefinite anticoagulant treatment is recommended after a first episode of pulmonary embolism occurring in the absence of a major reversible risk factor [125]. This evidence concerns the gene PROS1 and pulmonary embolism.