Protein S deficiency

Protein S deficiency

Description, Causes and Risk Factors:

Protein S is an anticoagulant that is normally present in blood. Protein S deficiency is inherited and results in an unusually low level of protein S in the blood. It is rare, occurring in about 1 in 500 people in Central Asia & Europe. Protein S deficiency can be inherited from one or both parents. This means that if one parent has it, then each child has a 50% chance of inheriting it.

Protein S is mainly synthesized in hepatocytes, but also in megakaryocytes, osteoblasts, and endothelial, Leydig and vascular smooth muscle cells, and circulates in plasma at a concentration of 20-25 mg/L/20-25 mg L-1. A de?ciency can be inherited or acquired because of vitamin K-antagonist therapy, oral contraceptives, pregnancy and various disorders, such as liver disease, nephritic syndrome, disseminated intravascular coagulation, and chronic infections (e.g. HIV).

Protein S deficiency is caused by mutations in the PROS1 gene. This gene provides instructions for making protein S, which is found in the bloodstream and is important for controlling blood clotting. Protein S helps block the activity of (inactivate) certain proteins that promote the formation of blood clots.

Most mutations that cause protein S deficiency change single protein building blocks (amino acids) in protein S, which disrupts its ability to control blood clotting. Individuals with this condition do not have enough functional protein S to inactivate clotting proteins, which results in the increased risk of developing abnormal blood clots. Protein S deficiency can be divided into types I, II and III based on how mutations in the PROS1 gene affect protein S.

Protein S deficiency is inherited in an autosomal dominant pattern, most people with protein S deficiency have inherited one copy of the abnormal protein S gene from one parent. There is a very rare chance (less than one in a million) of a child being born with two copies of an abnormal protein S gene. This condition causes severe problems with blood clotting leading to skin ulcers, blindness and organ failure shortly after birth.


Symptoms commonly associated with protein S deficiency are DVT (deep vein thrombosis), thrombophlebitis, and pulmonary embolism. Thrombosis under the age of 55 years or recurrent thrombotic episodes may also point to protein S deficiency. It is estimated that up to 80% of heterozygous patients will develop venous thromboembolism. Homozygous patients are at high risk for life-threatening purpura fulminans and disseminated intravascular coagulopathy.

The two common symptoms include:

    Pain or tenderness in the affected area.

  • Redness or swelling in the affected area.


    A family history is essential in assessing the association of a patient's deficiency with the patient's risk of thrombotic disease.

  • Laboratories can test protein s antigen as total antigen (includes protein-bound fraction) or free protein s antigen. Both free and total protein s are measured by ELISA.Functional assay for protein S deficiency should be considered if the other test results are normal and a reliable assay can be performed after excluding other interfering defects.

  • Coagulation tests: including aPTT, PT, fibrinogen level, fibrin degradation, d-dimer test.

  • Tests for other thrombotic risk factors, including anti-thrombin level, free protein s level, a plasma-based test for APC resistance, or a genetic test for factor V Leiden and prothrombin G20210A. Tests for plasminogen, dysfibrinogenemia, lupusanticoagulant and an anti-cardiolipin antibody may be required.

  • Investigation of thrombotic disease including Doppler, contrast venography, MRI, perfusion scan.


The primary goal of treatment is to prevent blood clots. The treatment you receive will depend on your history of previous blood clots, overall health, symptoms, and need for other medications or surgical procedures. The duration of treatment will vary depending on your individual medical history, and the presence of other health problems. Your treatment plan should be discussed with your PCP/Hematologist. Your doctor may recommend treatment with anticoagulant medications (blood thinners), such as heparin, low-molecular weight heparin, or warfarin to help prevent blood clots.

NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.

DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.


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