Protein S is a vitamin K-dependent anticoagulant protein. It functions as a cofactor of activated protein C to inactivate activated factor V (FVa) and activated factor VIII (FVIIIa). Its deficiency is a rare condition and can lead to deep vein thrombosis, pulmonary embolism or stroke. It is often treated with long-term anti-coagulant therapy.
Protein S deficiency may be hereditary or acquired; the latter is usually due to hepatic diseases or a vitamin K deficiency. Protein S deficiency manifests as an autosomal dominant trait; manifestations of thrombosis are observed in both heterozygous and homozygous genetic deficiencies of protein S. This case report is of DVT due to Protein S deficiency in a 53 year old male. Venous Doppler was used to diagnose DVT and free Protein S level measured by ELISA. IVC filter was placed on the third day of admission.
