Abstract

Background: The classification and outcomes of polyarticular and oligoarticular Juvenile Idiopathic Arthritis (p/oJIA) phenotypes are still ill-defined in the paediatric age and adulthood. The transition from the paediatric to the adult care is a crucial moment in the course of JIA. Predictors and outcomes of the of DMARD-treated p/oJIA population in adulthood are poorly characterised, as are the outcomes of the newly defined early onset ANA positive patients [1]. Objectives: Our primary aim was to describe the risk of relapse in a monocentric cohort of patients with o/pJIA and analyse the associated risk factors in order to define clinical endotypes of o/pJIA in adulthood. Methods: We prospectively collected clinical, serological, and demographic data of young adult patients (18-30 years old) referred to the transition clinic of a single centre between January 2020 and March 2023. Patients with systemic-onset JIA were excluded. Primary outcome was disease relapse, defined by Wallace criteria and the need of a therapeutic change. For each flare, tender joint and swollen joint counts were recorded, as well as C-reactive protein (CRP) level (mg/L). Disease activity 12 months prior to transition was evaluated retrospectively according to the same criteria. Patients who developed arthritis were compared to patients who maintained clinical remission up to the third year (36 months) of follow up in the transition clinic. Early onset ANA positive patients were also characterized. Risk factors for disease relapse were analysed by Cox proportional hazards regression with a 3 years time horizon. Results: Fifty o/pJIA patients with age 18-30 years old were enrolled in the study. The median age at disease onset was 6 years old (IQR 3-12) and the median disease duration at transition was 15 years (IQR 8.75-17.25). 21 patients were included in the early onset ANA positive subgroup. 21 (40%) patients were on csDMARDs and 39 (76%) were on biological DMARDs through adulthood. Approximately 30% of patients experienced some musculoskeletal disease activity in the 12 months prior to transition. Eighteen patients relapsed within 36 months after transition to adult care. Most relapses involved the knees (69.6%). The univariate analysis identified monoarthritis (HR 4.67, CI 1.069-20.41, p value=0.041) as the main risk factor for relapse within the first 36 months of follow-up. Early onset, ANA positivity, past and ongoing treatment with csDMARDs or bDMARDs, therapeutic withdrawal, and disease activity within 12 months before transition did not significantly influence the risk of relapse. Conclusion: In JIA patients the risk of relapse after transitioning to adult care remains high, irrespective of disease subtype and treatment. The main risk factor for the early occurrence of joint activity is monoarticular involvement, which may define a specific endotype of adult o/pJIA. The early onset ANA positive subgroup is not at higher risk of relapse compared with controls. REFERENCES: [1] Martini A, Ravelli A, Avcin T, Beresford MW, Burgos-Vargas R, Cuttica R, et al. Toward New Classification Criteria for Juvenile Idiopathic Arthritis: First Steps, Pediatric Rheumatology International Trials Organization International Consensus. J Rheumatol. 2019;46: 190–197. doi:10.3899/jrheum.180168. Acknowledgements: We thank Dr. Giacomo Cozzi, Dr. Mariagrazia Lorenzin, Dr. Antonio Collesei, Dr. Alessandra Meneghel for participating in patient management and their precious daily collaboration. Disclosure of Interests: None declared.