Purpose: Herpes zoster occurred in nine patients with methotrexate-treated rheumatoid arthritis. We compared these patients to a large group of methotrexate-treated rheumatoid arthritis patients in order to uncover potential factors explaining the occurrence of herpes zoster.
Patients and methods: Data from 187 patients taking methotrexate were reviewed and compared with data from another nine patients who developed herpes zoster while taking the drug for rheumatoid arthritis, all from the same university-based arthritis clinic. Literature pertinent to infection in rheumatoid arthritis patients treated with methotrexate is reviewed.
Results: Herpes zoster occurred in 14.5 cases per 1,000 patient-years in our methotrexate-treated rheumatoid arthritis patients, as compared with the general population incidence of 1.3 to 4.8 cases per 1,000 patient-years. The infection was unrelated to duration of methotrexate usage, prednisone treatment, or the co-existence of diabetes mellitus, but appeared to occur in patients with high titers of rheumatoid factor and an overall longer duration of rheumatoid arthritis. There were no cases of systemic dissemination or recurrence of herpes zoster despite 27.4 years cumulative follow-up on continued methotrexate therapy.
Conclusions: Herpes zoster may occur more frequently in patients with rheumatoid arthritis treated with low-dose methotrexate than in the general population. Herpes zoster in rheumatoid arthritis patients treated with methotrexate appears to be self-limited, benign, and statistically related to methotrexate use in the presence of longer-term rheumatoid disease.