Rheumatoid arthritis coexisting with ankylosing spondylitis: A report of 22 cases with delayed diagnosis.

Coexisting rheumatoid arthritis (RA) and ankylosing spondylitis (AS) in the same patient is often thought to be rare, and thus misdiagnosis is common. The aim of our study was to describe the main characteristics of RA coexisting with AS in patients with delayed diagnoses and improve awareness of the disease association.Between 2012 and 2018, data from 22 patients who had RA and AS (RA/AS) were retrospectively reviewed. All patients had a history of delayed diagnosis for RA or AS. The clinical features and radiographic changes of RA and AS patients were obtained at baseline and after 2 years. Disease activity score 28 (DAS28) or bath ankylosing spondylitis disease activity index (BASDAI) were used as outcome measures. The mean age at the time of diagnosis of RA/AS was 51.8 years, while the mean duration of diagnostic delay was 5.5 years. Middle-aged women were the most common subgroup among the RA/AS cohort. The common clinical manifestations were systemic, symmetric, peripheral, and axial arthritis. The erythrocyte sedimentation rate and C-reactive protein levels in RA/AS patients were elevated at the time diagnosis of RA/AS. The typical radiologic changes for the 2 diseases coexisted in RA/AS patients. The DAS28 and BASDAI scores at the 2-year follow-up evaluation were lower than the initial assessment.Coexisting RA and AS is often misdiagnosed for many years; a lack of recognition of RA and AS together is one of the most common reasons. Systemic, symmetric, peripheral, and axial arthritis in middle-aged women were the most frequent presentations at onset.