Background Juvenile idiopathic arthritis (JIA) is the most common chronic inflammatory arthritis 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 undifferentiated arthritis. Most paediatric inflammatory arthritides persist into adulthood. Therefore, a transition from paediatric 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 take control of their condition. The transition phase should be anticipated and structured because of the risk of failure in monitoring. However difference in classification criteria in paediatric and adult rheumatology can cause significant difficulty for adult rheumatologists.

Objectives The aim of this study was to determine the characteristics of juvenile-onset arthritis seen during the transition period and to compare paediatric classification criteria to those of adults.

Methods A retrospective bi-centre study was performed. Patients with JIA according to ILAR classification were included and had a consultation at transition. 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 112 patients were included: 17 systemic JIA, 26 polyarticular JIA, 19 oligoarticular JIA, 41 ERA and 9 psoriatic arthritis. The median age of transition was 19 years old. Eight cases of uveitis were observed among patients with oligoarticular JIA and 7 with ERA. Radiographic structural damages were assessed and showed 15% of patients with erosions or carpitis, mainly in polyarticular and systemic JIA patients. 29% of patients with ERA displayed sacroiliitis. In comparison with adult rheumatism, 42% of patients with systemic JIA fulfilled Yamaguchi criteria and 23% of patients with polyarticular JIA fulfilled ACR/EULAR criteria for RA. 41% of patients with oligoarticular JIA, 73% with ERA and 100% with psoriatic arthritis fulfilled ASAS criteria for spondyloarthritis.

Conclusions Our study confirmed the articular destructive potential of polyarticular and systemic JIA and an ocular risk in 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 paediatric entities. Finally, most patients with ERA and psoriatic arthritis fulfilled the ASAS criteria for spondyloarthritis.

Disclosure of Interest None declared