Protein S and congenital protein S deficiency: the most frequent congenital thrombophilia in Japanese.

Protein S is a natural anticoagulant. Congenital protein S (PS) deficiency is a confirmed risk factor of venous thromboembolism (DVT) which though occurs infrequently yet is a leading cause of maternal mortality and morbidity. Congenital PS deficiency may also be responsible for obstetric complications such as preeclampsia/eclampsia, recurrent fetal loss and intrauterine fetal restriction. Congenital PS deficiency has been identified in 1-7.5% of patients with DVT and in 0.03-0.13% general Caucasian population. However, Japanese people have higher prevalence both in VTE patients (12.7%) and general population (0.48-0.63%). Because PS deficiency is the most frequent congenital thrombophilia in Japanese people, Japanese obstetricians must understand this thrombophilia and also that women with PS deficiency have an increased risk of VTE and a necessity of prophylactic use of anticoagulant against recurrent VTE during pregnancy and puerperium. This article reviews the literature to understand PS and congenital PS deficiency, especially the association of this thrombophilia with pregnancy.