From the Guidelines
Low protein S activity means there is a reduced level of functional protein S in the blood, which is a natural anticoagulant that helps prevent excessive blood clotting. This condition increases the risk of developing abnormal blood clots, particularly in the deep veins of the legs (deep vein thrombosis) or lungs (pulmonary embolism) 1. Low protein S activity can be inherited (genetic) or acquired due to conditions like pregnancy, liver disease, vitamin K deficiency, oral contraceptive use, or certain medications. If you have low protein S activity, your doctor may recommend anticoagulant medications such as warfarin, heparin, or direct oral anticoagulants (DOACs) like rivaroxaban or apixaban, depending on your specific situation and risk factors 1. The dosage and duration of treatment will vary based on whether your condition is temporary or permanent. Some key points to consider include:
- Protein S works together with protein C to regulate blood clotting by inactivating clotting factors Va and VIIIa 1.
- When protein S levels are low, this regulatory mechanism is impaired, creating a hypercoagulable state where blood clots can form more easily than normal.
- The risk of thrombosis associated with thrombophilia, including protein S deficiency, is a significant concern, particularly in high-risk groups such as women using oral estrogen preparations, women who are pregnant, and patients undergoing major orthopedic surgery 1. It's essential to follow your doctor's recommendations and attend regular check-ups to monitor your condition and adjust treatment as needed.
From the Research
Definition of Low Protein S Activity
Low protein S activity refers to a condition where the levels of protein S, a vitamin K-dependent protein, are lower than normal in the blood. Protein S plays a crucial role in the regulation of blood coagulation, and its deficiency can increase the risk of thrombosis.
Causes and Associations
- Low protein S levels can be caused by genetic factors, as well as by certain medications such as warfarin 2.
- High factor VIII levels and low free protein S levels have been associated with an increased risk of arterial thrombosis 3.
- Low free protein S levels seem to be a mild risk factor for arterial thrombosis, and are not influenced by traditional arterial thrombotic risk factors such as hypertension, diabetes mellitus, and obesity 3.
Clinical Implications
- Protein S deficiency is an inherited thrombophilia associated with an increased risk of venous thromboembolism (VTE) 4.
- Unbalanced protein S deficiency due to warfarin treatment can be a possible cause for thrombosis 2.
- The use of direct oral anticoagulants (DOACs) may not be effective for the treatment of VTE in patients with protein S deficiency, due to lack of evidence 4.