Persistent arthritis develops in joints previously affected by palindromic flares: a longitudinal study investigating the transition from palindromic rheumatism to rheumatoid arthritis

OBJECTIVE: To assess whether joint involvement during palindromic rheumatism (PR) flares predicts future arthritis location in patients progressing to persistent inflammatory arthritis (PIA) and to compare rheumatoid arthritis (RA) features in patients with or without a PR prodrome. METHODS: In this single-centre longitudinal study, individuals at risk of RA from Leeds research cohorts who progressed to PIA were included. Demographics, clinical features and patient-reported outcomes were collected. In the PR cohort, joint involvement was recorded at initial flare, subsequent visits and at progression to PIA. Joint-level associations were analysed using cross-classified mixed-effects logistic regression model. Comparisons were made between patients with and without PR who eventually met 2010 American College of Rheumatology and European Alliance of Associations for Rheumatology RA criteria. RESULTS: 63 patients with PR progressed to PIA at a median of 13.4 months, with complete joint-level data for 48. Hands and shoulders were most affected at initial flare, with hands predominating across all flares. PIA developed in joints involved at any PR flare in 70.8% of patients. Prior involvement of a joint during a PR flare was associated with a higher risk of developing PIA in the same joint (OR 1.97, 95% CI 1.61 to 2.41; p<0.001). At RA diagnosis, patients with PR had lower Health Assessment Questionnaire and Visual Analogue Scale scores than those without PR, yet showed significantly higher swollen joint counts (4.1 vs 3.2; p=0.045). CONCLUSION: PR often begins in the hands and shoulders, and joint inflammation during PR usually precedes PIA in the same joints. Despite lower pain and disability, RA patients with PR show greater inflammatory joint burden at progression.