Protein C is a vitamin K dependent central protein in the Protein C pathway. Both genetic and acquired deficiencies of Protein C increase the risk of thrombosis. In homozygous Protein C deficiency (< 1% activity), individuals manifest neurologic and ophthalmic complications during intrauterine development and may have DIC. Approximately 4-8% Protein C deficiency is prevalent in thrombophilic population. The estimated thrombotic risk is 8-10 fold in patients with this deficiency. Congenital heterozygous Protein C deficiency may predispose to development of Coumarin associated skin necrosis. In Type I Protein C deficiency, the functional activity and antigenic levels are decreased to 50% of normal whereas in Type II deficiency the functional level is decreased to 50% of normal but the antigen level is 100% of normal.