UCAN CAN-DU: Canada-Netherlands Personalized Medicine Network in Childhood Arthritis and Rheumatic Disease

Inclusion Criteria: Cohort 1: - Biologic Basis of JIA * ≤18 years\* * Active objective arthritis suspected to be JIA or diagnosed with JIA within 6 months of enrolment * Treatment naïve except for NSAIDs, allowed to have received NSAIDS within 6 months of diagnosis Cohort 2 - Start Biologics * JIA diagnosis as per ILAR criteria (all subtypes) * ≤18 years\* * Active arthritis * For sJIA, active disease not necessarily with arthritis. * Time of start, restart or switch biologic therapy: e.g. failure, insufficient/partial response or intolerance Cohort 3 - Stop Biologics * JIA diagnosis as per ILAR criteria (all subtypes) * ≤18 years\* * Inactive disease * Discontinuing/tapering biologics for inactive disease Cohort 4: Extreme Phenotypes * Unexplained systemic inflammation with arthritis/arthralgia as a part of manifestations * High suspicion of genetic contribution * Severely affected patients with difficult to control disease (ie failure of multiple biologics) Exclusion Criteria: Cohort 1 : * Arthritis explained by another diagnosis * Joint injections as previous treatment less than 4 weeks prior to enrollment Cohort 2: * Arthritis explained by any other cause * Start on biologics as an indication for uveitis only Cohort 3: \- Tapering scheme \> 12 months to complete biologics stop Cohort 4: \- Arthritis explained by another diagnosis