An anonymous international electronic survey of 426 patients with self-reported idiopathic inflammatory myopathies (IIM) and myositis-related pain used latent class analysis (LCA) to identify distinct pain phenotypes, incorporating pain distribution, pattern, flare vs. current pain, and disease duration.
LCA identified 4 pain phenotypes: class 1 (proximal limb-predominant, lowest persistent pain, earlier disease, lowest fibromyalgia rates); class 2 (diffuse axial and proximal limb pain, intermediate fibromyalgia burden); class 3 (diffuse axial and distal-leg pain, intermediate fibromyalgia burden); and class 4 (widespread axial and extremity pain, highest persistent pain and fibromyalgia rates).
Self-reported diagnosis and pain without clinical verification; anonymous survey design prevents confirmation of IIM subtype or disease activity; cross-sectional design limits causal inference about phenotype progression.
Myositis-related pain is not uniform — clinicians should screen for fibromyalgia-like nociplastic patterns (especially widespread, persistent pain) in IIM patients, as these may require distinct management beyond standard immunosuppression.
