Fibromyalgia and Central Sensitization in Rheumatoid Arthritis, Psoriatic Arthritis, and Spondyloarthritis: A...

Fibromyalgia (FM) and central sensitization are increasingly recognized as clinically relevant in adults with inflammatory arthritis and spondyloarthritis, particularly when persistent pain and patient-reported symptoms complicate disease activity assessment. This systematic review synthesized clinical evidence on FM and central sensitization in adults with rheumatoid arthritis (RA), psoriatic arthritis (PsA), axial spondyloarthritis (axSpA), ankylosing spondylitis (AS), and other spondyloarthritis (SpA) populations. FM and central sensitization were treated as the primary concepts of interest. Related pain and sensory measures, including nociplastic pain features, neuropathic pain-like symptoms, reduced pressure pain thresholds, and quantitative sensory testing findings, were considered supportive evidence rather than equivalent measures of FM or central sensitization because they reflect different aspects of pain and sensory processing. A total of 47 primary reports met the eligibility criteria after a July 28, 2026 PubMed/MEDLINE update identified 12 additional eligible reports. Assessment approaches included FM diagnostic or classification criteria, FM screening instruments, Central Sensitization Inventory (CSI) measures, quantitative sensory testing, pressure pain thresholds, painDETECT, DN4, and related pain instruments. Across disease groups, FM and higher CSI-defined symptom burden were associated with higher symptom-sensitive composite disease activity scores, greater pain burden, fatigue, sleep disturbance, mood symptoms, impaired physical function, and poorer quality of life. Newer longitudinal and mechanistic studies also showed that pain sensitivity may change with disease-modifying therapy while objective inflammatory and sensory findings do not always move in parallel. Observational treatment-related evidence linked FM or higher symptom burden with difficult-to-manage or treatment-refractory phenotypes, remission classification, treatment retention, and biologic switching, without establishing causal treatment effects. Overall, FM and central sensitization-related symptom burden were frequently reported and were associated with higher symptom-sensitive disease activity scores and poorer patient-reported outcomes. Interpretation was most clinically relevant when symptom burden appeared disproportionate to objective inflammatory findings, while recognizing that active inflammation and amplified pain mechanisms may coexist.