Protein C
German physician Rudolf Virchow categorized abnormalities in the consistency of the blood as a factor in the development of thrombosis in 1856. The exact nature of these abnormalities remained elusive until the first form of thrombophilia, antithrombin deficiency, was recognized in 1965 by the Norwegian hematologist Olav Egeberg. Protein C deficiency followed in 1981, when described by researchers from the Scripps Research Institute and the U.S. Centers of Disease Control. Protein S deficiency followed in 1984, described by researchers at the University of Oklahoma.