OBJECTIVETo analyze the molecular pathogenesis of protein S deficiency in an adolescent case of recurrent deep vein thrombosis (DVT).

METHODSBlood samples from the patient and his family members were collected for detection of the coagulation parameters by one-step clotting method, and the protein S (PS) and protein C activities were measured by a chromogenic assay. Enzyme-linked immunosorbent assay was employed for detecting the levels of free PS antigen. All the exons and exon-intron boundaries of the patients PS gene were amplified using PCR and analyzed by direct sequencing.

RESULTSAs carriers of hereditary PS deficiency, both the patient and his father showed a heterozygous C82792T point mutation in the 10th exon of their PS gene which resulted in the substitution of arginine314 by cysteine in the polypeptide chain of PS protein.

CONCLUSIONRecurrence of DVT in this patient is the result of hereditary PS deficiency caused by a novel heterozygous missense mutation in the PS gene.