Later-onset rheumatoid factor negative polyarticular juvenile idiopathic arthritis (JIA): a unique patient group?

OBJECTIVES

To determine the two-year outcome of patients with later-onset polyarticular rheumatoid factor (RF) negative (-) juvenile idiopathic arthritis (JIA), and predictors of outcome.

METHODS

All patients ages 10 to16 years diagnosed and followed in the Rheumatology Clinic at SickKids Hospital with the diagnosis of polyarticular RF- JIA were eligible for study. A retrospective chart analysis was performed and number of active joints, medications, laboratory information and childhood health assessment questionnaire scores were recorded at diagnosis, and 6, 12, and 24 months following diagnosis.

RESULTS

As early as 6 months after diagnosis the mean number of active joints decreased from 16 to < 10, with 50% of the patients having < 5 active joints. The predominant joints affected were the wrist, knee, and small joints of the hand. The only predictor of active joint count at the 2-year follow-up was initial presenting active joint count as classified as mild, moderate, or severe. Sex, age, and laboratory results at presentation did not show any correlation with active joint count at 2 years. Majority of patients were treated with non-steroidal anti-inflammatory drugs (98%) and at least one disease-modifying anti-rheumatic drug (56%).

CONCLUSIONS

The two-year outcome of patients with late-onset RF- polyarticular JIA was very good with the majority of patients having minimally active disease at last follow-up. Presence of significant polyarthritis at presentation was the only feature associated with long-term joint activity. Sex and lab results did not show any correlation with active joint in this cohort of RF-JIA patients.