INCIDENCE, PREVALENCE AND POSSIBLE RISK-FACTORS FOR PNEUMONITIS IN PATIENTS WITH RHEUMATOID-ARTHRITIS RECEIVING METHOTREXATE

Objective. Methotrexate (MTX) is being used increasingly to treat rheu matoid arthritis (RA). Pneumonitis is a serious side effect of MTX the rapy (P-MTX). Our aim was to determine in patients with RA the inciden ce and prevalence of P-MTX in Western Australia and identify risk fact ors for the development of this adverse reaction. Methods. Patients wi th P-MTX were identified by (a) direct communication with rheumatologi sts in Western Australia, (b) use of a computerized clinical database, (c) questionnaire inquiry of all other rheumatologists in Australia. Possible risk factors for P-MTX were examined using age/sex matched ca se controls selected from the computerized clinical database. Results. Ten definite and 3 probable cases of P-MTX were identified. Local inc idence of P-MTX was 1/35.4 patient years MTX treatment; if definite an d probable cases are included (1149.6 patient years MTX treatment for definite cases alone). Twelve patients with P-MTX were compared with 2 4 age/sex matched controls. A shorter duration of MTX treatment and a higher incidence of preexisting lung disease were observed in P-MTX ca ses but these differences were not statistically significant. No diffe rence was observed between the P-MTX and control patients with respect to rheumatoid factor, duration of RA, use of tobacco, dose of MTX, se rum creatinine, creatinine clearance or concurrent treatment with aspi rin, nonsteroidal antirheumatic drugs or prednisolone. Conclusion. Our results indicate that in hospital clinic patients with RA pneumonitis is a common adverse reaction. They suggest that hypersensitivity is p robably responsible for most cases of pneumonitis associated with MTX, but preexisting lung disease may confer increased risk.