Background and purpose: Patients with rheumatoid arthritis may be prone to opportunistic infections. The aim of this study was to evaluate the levels of toxoplasma IgM and IgG antibodies in patients with rheumatoid arthritis.

Materials and methods: This cohort study was conducted in 286 rheumatoid arthritis patients. Blood samples were assayed for anti-toxoplasma IgM and IgG antibodies. The patients were followed up for six months. In addition, ESR, RF, Anticcp, and DSA28 levels were measured. Data analysis was done in SPSS, ver.18.

Results: We studied 286 rheumatoid arthritis patients of whom only 27 were positive for anti-toxoplasma IgM and IgG antibodies. According to the results, the mean levels of IgG and IgM were significantly different at the beginning of the study and after 6-month follow-up (P≤0.01 and P≤0.022, respectively).

Conclusion: As the findings of the present study indicated, patients with rheumatoid arthritis may be prone to toxoplasmosis. The six-month follow-up revealed that the treatment of this disease with immunosuppressive drugs increased the risk of toxoplasmosis. Consequently, patients with rheumatoid arthritis are vulnerable to opportunistic infections and should be carefully monitored.