Sandbox:Roukoz

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Roukoz A. Karam, M.D.[2]

Overview

Protein S deficiency is an autosomal dominant thrombophilia, which leads to an increased risk of thromboembolic events. Protein S is a vitamin K-dependent glycoprotein and plays a role in anticoagulation. It is mainly a cofactor to the activated protein C (APC), which inactivates coagulation factors Va and VIIa and thereby controlling the coagulation cascade.

Historical Perspective

Protein S was first discovered and purified in Seattle, Washington in 1979, and it was arbitrarily named protein S after the city it was discovered in. The function of this protein was still unknown; however, it was hypothesized that protein S plays a role in activating protein C. Protein S deficiency was first discovered in 1984 when two related individuals with recurrent thromboembolic events and normal coagulation tests were studied. At the time, protein C deficiency was usually associated with recurrent familial thrombosis. These individuals were found to have diminished anticoagulation activity with normal coagulation tests (including a normal protein C level), and when purified human protein S was added to their plasma, effective anticoagulation was restored. (1)