Background Juvenile idiopathic arthritis (JIA) is the most common chronic inflammatory rheumatism in children. The International League of Associations for Rheumatology 2001 (ILAR) classification includes 7 subgroups: systemic JIA, polyarticular JIA, oligoarticular JIA, enthesitis related arthritis (ERA), psoriatic arthritis and undifferenciated arthritis. Most pediatric inflammatory rheumatism persist into adulthood. Therefore, a transition from pediatric to adult rheumatology is a necessary step. Transition is defined as an active process by which a young patient with a chronic disease develops skills and resources to gradually assume his pathology. The transition phase should be anticipated and structured because of the risk of failure in monitoring. However difference in classification criteria in pediatric and adult rheumatism represents a major difficulty for adult rheumatologist.

Objectives The aim of this study was to determine the characteristics of juvenile-onset rheumatism seen during transition period and to compare pediatric classification criteria to adult criteria.

Methods A retrospective single-center study was performed. Patients with JIA according to ILAR classification were included and had transition visit. JIA classification criteria were compared to ACR/EULAR 2010 criteria for rheumatoid arthritis (RA), Yamaguchi criteria for adult Still's disease and ASAS criteria for spondyloarthritis.

Results 80 patients were included: 12 systemic JIA, 17 polyarticular JIA, 13 oligoarticular JIA, 29 ERA and 9 psoriatic arthritis. The median duration of disease was 7 years and the median age of transition was 19 years old. Six uveitis in oligoarticular JIA and 4 uveitis in ERA were observed as extra-articular manifestations. Radiographic structural damages were assessed and showed 12.5% of erosions and 7.6% of carpitis, mainly in polyarticular and systemic JIA patients. 39.3% of patients with ERA displayed sacroiliitis. In comparison with adult rheumatism 42% of patients with systemic JIA fulfilled Yamaguchi criteria and 29% of patients with polyarticular JIA fulfilled ACR/EULAR criteria for RA. 54% of patients with oligoarticular JIA, 76% with ERA and 100% with psoriatic arthritis fulfilled ASAS criteria for spondyloarthritis. In addition 78.75% of patients were in remission and 70% of patients were treated with biotherapy.

Conclusions Our study confirmed an articular destructive potential of polyarticular and systemic JIA and an ocular risk of oligoarticular JIA. Comparison of JIA criteria to adult rheumatism criteria showed that polyarticular JIA with positive rheumatoid factor fulfilled ACR/EULAR criteria for RA. However, oligoarticular JIA and polyarticular JIA without rheumatoid factor did not fulfill any adult rheumatism criteria and seem to be pediatric entities. Finally, most of patients with ERA and psoriatic arthritis fulfilled ASAS criteria for spondyloarthritis.

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Disclosure of Interest None declared