Expressions of PGD2 and hPGDS were inversely associated with serum C-reactive protein (P < 0.01) and erythrocyte sedimentation rate (P < 0.01).The findings suggest that synovial DCs may be an important source of hPGDS and that systemic disease activity may be influenced by actions of PGD2 in RA and other arthropathies. Here, PTGDS is linked to rheumatoid arthritis.