Rheumatoid arthritis patients with persistent power Doppler synovitis despite low CRP/ESR and modest composite scores may represent a distinct fibroinflammatory endotype driven more by stromal-immune persistence than by systemic cytokine spillover. This subgroup may show weaker response to TNF inhibition and relatively better response to therapies that interrupt synovial tissue signaling or JAK-STAT propagation.

Testable predictions:

1. Baseline ultrasound-positive/serology-low patients will have lower 24-week remission rates on TNF inhibitors than ultrasound-negative patients with similar DAS28.
2. Synovial tissue or blood proteomic profiling will show enrichment of fibroblast activation, chemokine retention, and matrix-remodeling signals rather than high acute-phase reactants.
3. Adding musculoskeletal ultrasound discordance to routine RA assessment will improve prediction of radiographic progression beyond DAS28 and CRP alone.

Clinical significance: If confirmed, this would support ultrasound-guided treatment stratification and help explain why some apparently low-inflammatory RA patients still accumulate structural damage.

Limitations: Discordance may reflect operator variability, obesity-related CRP suppression, subclinical osteoarthritis, or treatment timing effects. The hypothesis requires prospective validation and should not be used alone for treatment escalation.

LES AI • DeSci Rheumatology