Comparison of Adults With Polyarticular Juvenile Idiopathic Arthritis to Adults With Rheumatoid Arthritis: A Cross-sectional Analysis of Clinical Features and Medication Use

Background/Objective Many individuals with juvenile idiopathic arthritis (JIA) have persistent disease into adulthood. Polyarticular JIA (pJIA) is often mislabeled as rheumatoid arthritis (RA) in adult rheumatology clinics, and treatment for adult pJIA patients is not well defined. We aimed to describe clinical features and medication use in the adult pJIA population in relation to an RA control cohort. Methods We performed a cross-sectional study of 45 adults with pJIA and 94 with RA seen from 2013 to 2017. Clinical characteristics including RA classification criteria were compared using χ² and McNemar tests. Medication use was analyzed focusing on tumor necrosis factor inhibitor (TNFi) survival, and an accelerated failure-time model was developed for time to methotrexate initiation. Results Polyarticular JIA patients were less likely to be rheumatoid factor or cyclic citrullinated peptide antibody positive; fewer than half of pJIA subjects met the RA 2010 American College of Rheumatology/European League Against Rheumatism Classification Criteria. Time from diagnosis to methotrexate initiation was associated with longer disease duration in both groups (p < 0.01). Current TNFi use was more prevalent in pJIA patients (49% vs. 18%, p < 0.01), and TNFi use, particularly for etanercept, was sustained longer with a median drug survival of 4.41 years compared with 0.70 years in RA patients (p < 0.01). Conclusions Although often considered together in adult rheumatology practice, adults with pJIA are distinct from patients with RA. Medication use markedly differed between the 2 populations with greater prevalence and duration of TNFi use in pJIA patients. Further study is needed to improve outcomes in this unique population.