[Clinical relapse of rheumatoid arthritis (escape phenomenon) during low-dose methotrexate therapy].

Objective: To clarify the incidence and background of clinical relapse (escape phenomenon) during low-dose methotrexate therapy for rheumatoid arthritis.

Methods: Seventy one patients with rheumatoid arthritis (RA) were analyzed. They were started on therapy with methotrexate (MTX) between April 1, 1991 and May 30, 1995. Among them, 60 patients showed clinical improvement within 6 months after the start of the therapy and were subjected to the analysis for clinical relapse (escape phenomenon).

Results: Twelve patients showed an initial improvement followed by a relapse with increased serum CRP and number of painful joints despite the MTX therapy was continued. Two types of the relapses were seen; (1) early, escape (relapse after an initial brief improvement) in 7 patients, and (2) late escape (relapse after a long-term improvement with MTX therapy) in 5 patients. The early escape was seen at 9.0 +/- 0.7 months after the start of therapy while the late escape was seen at 23.3 +/- 4.8 months. Patients with both types of escape phenomenon had the longer duration of the disease and more advanced stage. There was no relationship between clinical relapse and age, baseline RA activity, MTX dose, or concurrent use of corticosteroids and other disease modifying anti-rheumatic drugs. The efficacy of MTX for RA was restored by increasing dose of MTX in 11 patients.

Conclusion: These results suggest that clinical relapse is not rare in RA patients during low-dose methotrexate therapy, but could be improved by increasing dose.