Reactive arthritis is an acute, nonsupurative oligoarthritis that are frequently seen in men, between 15 and 60 years of age and that is developed after the infection localized in other region in the body and the causative microorganism can not mostly be determined in the synovium. Many microorganisms such as Salmonella, Shigella, Yersinia and Chlamydia trachomatis playing role in gastrointestinal and genitourinary infections. In this study, C. trachomatis Ag in synovial fluid, and C. trachomatis IgG and IgM in serum were investigated by Enzim Immuno Assay (EIA) in 32 patients that is diognosed reactive arthritis by clinical examination (study group). 29 asemptomatic patient samples were studied as control group. C. trachomatis Ag, IgG and IgM were found positive in 4 (12.5%), 22 (%68.8) and 12 (%37.5) of 32 patients respectively, in study group. In control group, IgG and IgM were found positive in 1 (%3.4) and 17 (%58.6) of 29, respectively. However, C. trachomatis Ag was not found positive in control group. No other microorganism was found in all groups, and rheumatologic markers were negative. Independent sample T test, Pearson X2 and Fisher's X2 tests were used for statistical analysis. In study group, the relations between reactive arthritis and the positivity of the C. trachomatis Ag and Ig M was found statistically significant.

As a conclusion, C. trachomatis is an important pathogenic microorganism in reactive arthritis etiology, however, the role of C. trachomatis in the etiology of reactive arthritis should be investigated with molecular techniques in wide series.