Altered somatosensory profiles in rheumatoid arthritis, psoriatic arthritis, axial spondyloarthritis, and systemic sclerosis.

Objectives: This exploratory study aimed to examine the somatosensory profiles of patients with rheumatoid arthritis (RA), psoriatic arthritis (PsA), axial spondyloarthritis (axSpA), and systemic sclerosis (SSc) using quantitative sensory testing (QST). We sought to identify distinct patterns of sensory alterations to enhance the understanding of pain mechanisms in these conditions and to generate hypotheses for future mechanistic research and therapy approaches. Methods: Patients with RA, PsA, axSpA, and SSc underwent QST on both hands to evaluate all somatosensory submodalities. Standardised assessment, following the German Research Network on Neuropathic Pain protocol, included mechanical detection threshold (MDT) and vibration detection threshold (VDT) as well as thermal detection and pain thresholds. Results: We enrolled 80 patients (20 with RA, PsA, axSpA, SSc) and 20 controls. Significant differences in MDT (RA: Conclusions: Patients with RA, PsA, axSpA, and SSc demonstrate significant alterations in somatosensory processing, including abnormal MDT and VDT, and pathological allodynia that appear independent of inflamed areas. These sensory changes do not correlate with disease activity, duration, inflammatory markers, or therapeutic approach, indicating that they may result from mechanisms distinct from inflammation.