Pain in Axial Spondyloarthritis: More to It Than Just Inflammation

The conceptual paradigm of axial spondyloarthritis (axSpA) has evolved and now comprises an expanded spectrum that includes more females and patients with little or no radiographic changes in sacroiliitis or syndesmophyte formation in the spine.1 This broadened paradigm is often, but not always, characterized by an inflammatory magnetic resonance imaging (MRI) signature. Multiple studies have demonstrated a similar burden of symptoms, physical dysfunction, and disability across the full spectrum of disease presentation, regardless of the presence of radiographic damage, including pain.2,3,4 Does the pain experienced by these patients only represent a summation of arthritis, enthesitis, and osteitis, both axial and peripheral (i.e., purely induced by inflammation and structural damage), or could there be broader pathologic processes that contribute to and amplify the pain experience? Studies have shown that in a substantial proportion of patients with axSpA, as well as other chronic inflammatory diseases,5 some of the pain and other symptoms such as fatigue represent fibromyalgia (FM) or analogous terminology: chronic widespread pain (CWP), central sensitization, "fibromyalgianess," or the newest term, "nociplastic pain."6 The conditions these terms denote are not fully synonymous, but all allude to the phenomenon of increased nociception mediated through the central nervous system. The proportion of pain that is mediated by the underlying inflammatory condition, the "-itis", vs the centrally mediated pain condition, the "-algia," often varies depending upon such factors as the patient's sex, the effectiveness of immunomodulatory treatment of the inflammatory disease, disease duration, genetic risk for central sensitization, and other contextual factors.7 Since the degree of central pain can confound our ability to measure the degree of inflammatory pain, how can we more accurately assess their relative contributions so as not to undertreat or mistreat the "-itis" component and overtreat or mistreat the "-algia" component? … Address correspondence to Dr. M.N. Magrey, 2500 MetroHealth Drive, Cleveland, OH 44109, USA. Email: mmagrey{at}metrohealth.org.