A novel mutation Gly222Arg in PROS1 causing protein S deficiency in a patient with pulmonary embolism

Background Thrombophilia is becoming a more frequently reported disorder these years. Hereditary protein S deficiency is one of the anticoagulant deficiencies that eventually results in thrombophilia. Case presentation A 24‐year‐old male patient was suffering from unexplained thrombosis for the second time with a family history of deep venous thrombosis. Screening tests for anticoagulant proteins found the activity of protein S markedly lowered (5.0%). The patient was discharged after anticoagulation treatment. Four years later, the review still showed the activity of protein S in his plasma decreased (16.0%). Molecular genetic analysis revealed him homozygous for a missense mutation, c.664G>A, in the exon7 of PROS1 . The mutation discovered here is the first mutation affecting the codon 222 of PROS1 . This mutation results in the replacement of the glycine at the codon 222 of protein S with arginine, leading to a reduction of protein S function. Conclusions The finding of this mutation may help with the understanding of the mechanism of protein S deficiency, especially in the Chinese population.