Abstract: Objective: To determine the association between mycoplasma infection and rheumatoid arthritis. Methods: The patients with rheumatoid arthritis treated in our hospital from January 2017 to December 2017 were collected. Ureaplasma urealyticum (Uu), Mycoplasma arthritis (Mar), Mycoplasma hominis (Mh) and Mycoplasma fermentans (Mf) were detected by PCR. Results: The positivity rates of Uu, Mh, Mar and Mf were 22.5%, 14.2%, 0.8% and 0.8% in pharyngeal swabs, respectively, and were 31.6%, 21.1%, 3.5% and 0.0% in urethral swabs, respectively. The positivity rates of Uu, Mh, Mar and Mf were 11.6%, 4.7%, 2.3% and 0.0% in joint fluid, respectively. The positivity rates of Uu, Mh, Mar and Mf were 45%, 10%, 5% and 0.0% in cervical swabs, respectively. There were significant differences in lower bone mineral density, joint disease activity score (DAS) of 3.2-5.1 and DAS>5.1 between the Uu positive and negative patients (P<0.05). Conclusion: Ureaplasma urealyticum may be associated with the severity of rheumatoid arthritis.

Key words: mycoplasma infection, rheumatoid arthritis, pathogenesis