A novel PROS1 mutation, c.74dupA, was identified in a protein S deficiency family.

Protein S is a vitamin K-dependent plasma glycoprotein that acts as an anticoagulant, and its deficiency usually predisposes individuals to venous thromboembolism. Hereditary protein S deficiency is an autosomal dominant disorder caused by a PROS1 mutation. Herein, we described a novel PROS1 frameshift mutation, c.74dupA, in a hereditary protein S deficiency family. Interestingly, both of the proband and his mother carried the mutation and had a protein S deficiency, however, only the proband suffered a pulmonary embolism while his mother had no history of any thrombosis, suggesting that a triggering event might have been involved in the thrombus formation. Therefore, genetic testing of PROS1 appeared important for the early diagnosis of hereditary protein S deficiency, and it allowed the application of prophylactic interventions to prevent the incidence of severe thrombosis.