PROS1 and thrombophilia: Previous studies have shown that aging, long-term immobilization, trauma, cancer, virus infection, and genetic risk factors such as classical thrombophilia: factor V Leiden (rs6025) and prothrombin G20210A mutation (rs1799963), and deficiencies of antithrombin, protein C, and protein S contribute to VTE risk (Gohil, Peck et al. 2009; Crous-Bou et al. 2016).