Protein S Deficiency Presented as Pulmonary Artery Thromboembolism: A Case Report and Literature Review

Abstract Background: Protein S is a rare vitamin K-dependent plasma glycoprotein that deactivates activated coagulation factors Va and VIIIa to disrupt secondary hemostasis. Protein S deficiency is an autosomal-dominant hereditary clotting condition linked to recurrent and spontaneous venous thrombosis. In their early adult years, patients typically have pulmonary embolism and spontaneous, recurrent deep vein thrombosis.This case should be reported due to the rarity of the congenital disease being considered and the efficacy of alternative therapy such as IVC filters. Case presentation: We present the case of a 34-year-old Chinese man who experienced his first thrombotic episode in his pulmonary arteries. Protein S deficiency was revealed by thrombophilia screening. The patient rejected the recommendation to implant an inferior vena cava filter. The patient declined implantation of an inferior vena cava filter and received rivaroxaban and blood thinners to maintain stability. After 349 days of follow-up, the patient still had pulmonary embolism. Conclusions: Although protein S deficiency is a rare cause of arterial thrombosis, it should still be considered because of its potential for recurrence and progression to more severe stages, particularly in East Asian populations.