Outcomes of undifferentiated peripheral inflammatory arthritis in real-world practice. A longitudinal cohort study.

Although the majority of UIPA cases treated with step-up combination therapy with DMARDs do not progress to RA, most require continued treatment and a few achieve medication-free remissions. Key Points • Undifferentiated peripheral inflammatory arthritis (UPIA) can progress to rheumatoid arthritis in 11% of cases; and lack of sustained remission, being anti-citrullinated peptide antibody positive, non-adherence to therapy, and having flare are its predictors. • Medication-free remissions occur in 21% of patients with UPIA; and absence of comorbidity, starting a sustained remission at ≤ 6 months, and having no flare are its predictors. • Initiating treatment in the window of opportunity may lead to a better joint outcome.