ABSTRACT
OBJECTIVE: To see whether the active inflammation in Behcet's disease (BD) can cause thrombotic disorders by decreasing the protein S activity (PSA), we evaluated the relationship between PSA decrease and disease activity of BD. METHODS: We included 122 patients with BD whose PSAs were measured between August 1998 and April 2005. In 51 BD patients, the PSA was measured again when there were changes in the number of items of "The Behcet's Disease Current Activity Form (BDCAF)". RESULTS: Thrombosis rate was 2.5% (3/122), and the PSA was low in all 3 of the patients. The incidence of low PSA in total 122 BD patients was 27% (33/122). The incidence of low PSA in active BD patients was 33.7% (31/92), and it was significantly more frequent in active BD patients than in inactive patients, 6.7% (2/30) (chi2-test, p value=0.0038). The decrease of PSA had good correlation with the number of BDCAF items (r=-0.351, p=0.012). CONCLUSION: The PSA decrease is related to the disease activity of BD. PSA could be not only the risk factor for thrombotic disorder but also the activity marker for the BD and other inflammatory diseases.