Residual disease in axial spondyloarthritis. Facts and issues.

Residual disease in axial spondyloarthritis (axSpA) is defined by the persistence of signs, symptoms, or disease burden despite active treatment. Magnetic resonance imaging (MRI) inflammation may still be present in up to one-third of patients in clinical remission. Moreover, residual symptoms are frequently reported in patients with low disease activity (LDA), with 20-40% of patients experiencing pain or fatigue scores greater than 4 out of 10 on a visual analogue scale. Nociplastic pain (central sensitization) and neuropathic pain components are commonly associated with residual symptoms, as is female gender. Other contributing factors may include psycho-behavioral disorders, low physical activity, sarcopenia, sleep disturbances, and comorbidities. This residual disease is a key feature of difficult-to-manage (D2M) axSpA. A comprehensive assessment of the patient's context and a thorough evaluation of pain mechanisms are essential first steps in the management of these patients. Non-pharmacological strategies should be prioritized and reinforced in this setting, while certain targeted disease-modifying anti-rheumatic drugs (DMARDs) may have a specific effect on pain independently of their anti-inflammatory properties. There is a pressing need for new biomarkers that more specifically reflect the inflammatory process in spondyloarthritis, as therapeutic response is currently assessed primarily through patient-reported outcomes (PROs). Although no consensus definition exists to date, the recognition of residual disease and its associated factors is crucial in axSpA - particularly in a condition where objective signs of inflammation may be absent - to prevent overtreatment.