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Extracapsular and joint-dominant hand and wrist MRI patterns in psoriatic and rheumatoid arthritis: an exploratory case-control study

Year: 2026

Type: article

Abstract: Background: Psoriatic arthritis (PsA) and rheumatoid arthritis (RA) may present with overlapping hand and wrist symptoms, while their anatomical patterns of inflammation differ. Objective: To compare prespecified hand and wrist magnetic resonance imaging (MRI) features between PsA and RA and to assess selected exploratory associations, discriminatory performance, anatomical distributions and reader reliability. Methods: This retrospective case-control study included 41 patients with PsA and 41 with RA who underwent clinically acquired 3.0-T hand or wrist MRI. Research MRI features were assigned retrospectively by readers blinded to the clinical diagnosis. Between-group comparisons used available-case denominators. Each adjusted model included one MRI feature together with age, sex and symptom duration; Firth bias-reduced logistic regression was used for the sparse vascular-like signal feature. Results: Compared with RA, PsA had higher median scores for extracapsular soft tissue inflammation (7 vs. 2), periarthritis (8 vs. 4) and bead-like peritendinous effusion (1 vs. 0; all P <0.01). Study-defined prominent reticular vascular-like signal occurred in 35/41 patients with PsA and 2/41 with RA and showed a strong but imprecise adjusted association with PsA (odds ratio 85.02, 95% CI 15.07-479.83). RA had a higher median joint effusion score (5 vs. 2) and more frequent wrist synovitis (33/41 vs. 7/37) and wrist bone erosion (30/41 vs. 8/39; all P <0.01). Inter-reader coefficients ranged from 0.574 to 0.914 and intra-reader coefficients from 0.846 to 0.968. Limitations: The historical screening denominator and formal composite disease activity scores could not be reconstructed; one clinically diagnosed RA case did not meet the retrospective classification threshold; treatment exposure differed between groups; distal interphalangeal and ulnocarpal coverage was incomplete; and external validation was not performed. Conclusion: In this exploratory cohort, extracapsular and enthesis-associated MRI findings favored PsA, whereas joint effusion and wrist synovitis or erosion favored RA. The study-defined vascular-like and bead-like features require independent validation before clinical use.

Source: Frontiers in Immunology

DOI: 10.3389/fimmu.2026.1945180