The association of Mycoplasma hominis with arthritis.

The facts that mycoplasmal arthritis occurs naturally in various animal species and can be induced experimentally have been the main reasons for searching for evidence of mycoplasmal infection in the joints of patients with rheumatoid arthritis. There is, however, no evidence that Mycoplasma hominis is involved in this disease. On the other hand, M. hominis and other mycoplasmas, including Ureaplasma urealyticum, have been isolated from the arthritic joints of several hypogammaglobulinemic patients, and there is some evidence to indicate that the organisms are responsible for the disease. Furthermore, on rare occasions M. hominis has caused arthritis in mothers after childbirth. The relationship between this agent and sexually acquired reactive arthritis (SARA) has been the subject of recent investigation. Sera from 27 patients with nongonococcal urethritis and 25 patients with SARA, all tested previously for antibody to Chlamydia trachomatis, were examined by a metabolism-inhibition technique for antibody to M. hominis. Interpretation of the first tests was difficult because tetracyclines given to some of the patients caused their sera to inhibit metabolism. This problem was overcome by use of a tetracycline-resistant strain of M. hominis. Antibody was found in the sera of only a few patients and not in those of SARA patients whose disease was considered to be nonchlamydial. The initiating factor in nonchlamydial SARA therefore remains an enigma.