Superior mesenteric venous thrombosis associated with a familial missense mutation (Pro626Leu) in the SHBG-like domain of the protein S molecule.

A 76-year-old Japanese woman was hospitalized for ileus symptoms caused by extensive thrombosis of the superior mesenteric vein. Because laboratory test results suggested type III protein S (PS) deficiency, molecular changes in PS were investigated. A single-base transition, CCG to CTG at codon 626 in exon XV, resulting in the missense mutation Pro626Leu, was identified in an allele of the patient and in her son. Reverse transcriptase polymerase chain reaction analysis indicated the presence of both normal and mutant types of PS messages in platelet-derived messenger RNAs. Our findings thus suggest that Pro626 in SHBG-like domain 7 may be crucial for in vivo antithrombotic activity of the PS molecule.