PROTEIN S DEFICIENCY
Protein S is another natural anticoagulant normally produced in the liver. APC requires Protein S to inactivate certain clotting fac-tors. When the level of Protein S is deficient, this inactivation process is diminished, and the risk for thrombosis can be increased. Like patients with Protein C deficiency, those with Protein S defi-ciency have a greater risk for recurrent venous thrombosis at a young age, as young as 15 years.