Characterizing arthritis subtypes in lupus: prevalence, clinical features and role of type I interferon signatures.

OBJECTIVES

Arthritis is a common manifestation of systemic lupus erythematosus (SLE). We examined the prevalence and associations of arthritis subtypes in SLE, focusing on associations with type I interferon (IFN) scores.

METHODS

In this observational cohort study at the University of Toronto Lupus Clinic (July 1970-August 2024), arthritis was defined clinically as non-deforming arthritis (NDA), Jaccoud's arthropathy (JA) and arthritis with clinically irreducible deformities (CIDA). Univariable and multivariable (MV) logistic regression was used to assess associations with arthritis subtypes with NDA as reference in the prevalent cohort and subgroup with available IFN scores (reported as high/low).

RESULTS

Among 2264 patients, 1248 (55.1%) had arthritis: 908 (72.8%) had NDA, 239 (19.2%) JA, and 101 (8.1%) CIDA. In the multivariable logistic regression analysis, JA was associated with longer disease duration (odds ratio [OR] 1.05 [95% CI: 1.03, 1.08]) and female sex (2.06 [1.11, 3.83]) whereas CIDA was associated with neurological involvement (1.79 [1.13, 2.84]), anti-Ro antibodies (1.71 [1.01, 2.90]), higher adjusted mean joint count (1.09 [1.03, 1.77]) and lower adjusted mean SLEDAI-2K over follow-up (0.89 [0.81, 0.98]) compared with NDA. In patients with available IFN scores (n = 475), CIDA was associated with a low IFN signature in unadjusted analysis, whereas both JA and NDA had a high IFN signature.

CONCLUSION

Distinct clinical and serological patterns differentiate JA and CIDA, suggesting unique underlying mechanisms of deforming arthritis in SLE. Both NDA and JA exhibited a high IFN signature, while CIDA showed a higher joint burden, lower disease activity and lower IFN signature relative to NDA.