Do minocycline and other tetracyclines have a place in rheumatology?

Tetracyclines are a family of antimicrobials with activity against a broad range of organisms including those that develop intracellularly. Links have been reported between some infections and some inflammatory joint diseases, with the most notable example involving mycoplasmas and rheumatoid arthritis. Reactive arthritides are known to be triggered by organisms found in the gastrointestinal or genitourinary tract, and antigenic material from these organisms has recently been demonstrated in synovial tissue from patients with reactive arthritis. These facts led to the hypothesis that tetracyclines may be useful in rheumatoid arthritis and reactive arthritis. Two controlled studies found that minocycline benefited rheumatoid arthritis patients when it was given either as an adjunct to another second-line treatment or as the only slow-acting drug. Lymecycline has been found to expedite recovery from reactive arthritis due to Chlamydia trachomatis, and tetracycline to decrease the incidence of reactive arthritis due to sexually-transmitted diseases. The safety profiles of these treatments were acceptable in all available studies but require further investigation during long-term administration. The benefits may be related to the immunomodulating effects of tetracyclines and/or to their ability to inhibit metalloproteases such as collagenases. Whether tetracycline therapy influences the course of radiologic lesions in rheumatoid arthritis remains unknown. However, minocycline therapy has given sufficient proof of its efficacy to make it an attractive alternative in rheumatoid arthritis.