Navigating the complexity of pain in psoriatic arthritis and axial spondyloarthritis.

Abstract

Pain is the most common and often most troublesome feature of chronic autoimmune diseases such as psoriatic arthritis (PsA) and axial spondyloarthritis (AxSpA). A predominant concept is that the main source of pain is from disease-induced tissue inflammation and structural damage, activating peripheral nerve fibers which relay to the central nervous system. This mechanism is nociceptive pain and the presumption has been that controlling inflammation will be sufficient to reduce this form of pain. However, despite control of inflammation, patients may still have significant residual pain. We are learning that there are additional pain mechanisms, neuropathic and nociplastic, that are often operative in patients with rheumatologic conditions, that can significantly influence pain experience, quantitation of disease activity, and may benefit from therapeutic approaches distinct from immunotherapy. Neuropathic pain arises from diseased or damaged nerve tissue and nociplastic pain reflects sensitization of the central nervous system due to multiple genetic, neurobiologic, neural network dysregulation, and psychosocial factors. Pain arising from these mechanisms influence assessment of disease activity and thus needs to be factored into decision-making about immunotherapy efficacy. This review addresses the importance of accurately assessing the complex mechanisms of pain experience in patients with PsA and AxSpA to more appropriately manage immunomodulatory, neuromodulatory, and nonpharmacologic therapies.