Portal-Splenic-Mesenteric Venous Thrombosis in a Patients with Protein S Deficiency due to NovelPROS1Gene Mutation

Protein S (PS), a vitamin K-dependent glycoprotein, performs an important role in the anticoagulation cascade as a cofactor of protein C. Because of the presence of a pseudogene and two different forms of PS in the plasma, protein S deficiency (PSD) is one of the most difficult thrombophilias to study and a rare blood disorder associated with an increased risk of thrombosis. We describe a unusual case of previously healthy 37-year-old man diagnosed with portal-splenic-mesenteric vein thrombosis secondary to PSD. The patient was admitted to the hospital due to continuous nonspecific abdominal pain and nausea. Abdominal computed tomography revealed acute venous thrombosis from inferior mesenteric vein to left portal vein via splenic vein, and laboratory test revealed decreased PS antigen level and PS functional activity. Conventional polymerase chain reaction and direct DNA sequencing analysis of the PROS1 gene demonstrated duplication of the 166th base in exon 2 resulting in frame-shift mutation (p.Arg56Lysfs*10) which is the first description of the new PROS1 gene mutation to our knowledge. Results from other studies suggest that the inherited PSD due to a PROS1 gene mutation may cause venous thrombosis in a healthy young man without any known predisposing factor.