Definition
Protein S deficiency is a congenital disease of the body’s own blood clotting system, which is caused by a deficiency of the anticoagulant protein S. This disease is relatively rare with a prevalence of approximately 0.7 to 2.3% in the normal population. Protein S is usually produced in the liver and, together with other anticoagulant factors, ensures that the formation of a blood clot is restricted to the site of the vascular injury. If a deficiency of this protein occurs, the factors responsible for blood clot formation predominate, so that the clinical picture is associated, for example, with an increased tendency to form clots within intact blood vessels. Patients have an increased risk of suffering from leg vein thrombosis or acute occlusion of any blood vessel caused by a clot. This clot (thrombus) can also occlude vital vessels, so that a deficiency/shortage of supply to dependent organs can lead to tissue loss, for example in the heart, lungs, brain or intestine.
Are there different forms of the disease?
In principle, the clinical picture of the patient is independent of the presence of the various subtypes. However, we speak of three subtypes that can be distinguished diagnostically:
- Type I: Characteristic of type I is that the activity of the present protein S is reduced; in addition, the concentration of the total protein and the free (active) protein in the blood is also reduced. By definition, a Type I is present when the amount of free protein falls below 40% of the normal value.
- Type II: A type II deficiency is present when only the activity of the protein S is reduced but the concentrations of total and free protein are unchanged.
- Type III: Patients with normal levels of total protein S, but with reduced levels of free protein (< 40%) and dysfunction of free protein, suffer from type III protein S deficiency.
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