Ongoing disease activity and changing categories in a long‐term nordic cohort study of juvenile idiopathic arthritis

Objective To describe the disease characteristics, long‐term course, and outcome of patients with juvenile idiopathic arthritis (JIA) in a population‐based setting. Methods Consecutive cases of JIA from defined geographic areas of Denmark, Finland, Sweden, and Norway in whom disease onset occurred in 1997–2000 were included in a prospective, multicenter cohort study. The study was designed to be as close to a population‐based study as possible, with centers participating only if they were able to include in their catchment area all children in whom JIA was diagnosed. Results Of 500 children included, 440 (88.0%) had repeated visits, with the last visit occurring at least 7 years after disease onset (median 98 months, range 84–147 months). Changes in the International League of Associations for Rheumatology category were observed in 10.8% of the children, and, in addition, extended oligoarthritis developed in 34.7% of the group with oligoarticular JIA. During the observation period, 58.0% of the children were treated with disease‐modifying antirheumatic drugs, including biologic medications. Ongoing disease activity was mostly mild, but some JIA‐related damage developed in 22.9% of the children. At the last followup visit, remission off medication was observed in 42.4% of the children, 8.9% were in remission on medication, and 48.7% were not in remission. The highest rates of remission were observed in patients with persistent oligoarticular JIA and in those with systemic JIA. Conclusion In this long‐term prospective study of JIA in a population‐based Nordic setting, ongoing disease was evident in a majority of the children. The present results underline the need to identify early predictors of outcome, to further improve therapy, and to continue long‐term followup of patients with JIA.