PROS1 and thrombophilia: A comprehensive thrombophilia workup, including tests for anticardiolipin antibodies, homocysteine levels, protein C, protein S, anti-beta2 glycoprotein-I antibodies, and genetic testing for thrombophilia mutations (polymorphic variants G1691 A of factor V, G20210A of prothrombin, and C677T of methylentetrahydrofolate reductase), yielded negative results.