Immunological profiling and treatment patterns of primary Sjögren's disease patients with concomitant rheumatoid arthritis: a retrospective cohort study.

BACKGROUND: The coexistence of primary Sjögren's disease (pSS) and rheumatoid arthritis (RA) is not uncommon, but its immunological characteristics and treatment patterns remain poorly defined. This study aimed to compare the immune profiles and therapeutic strategies between pSS patients with and without RA overlap. METHODS: A total of 148 patients with pSS were retrospectively enrolled, including 89 without RA and 59 with concomitant RA. Demographic characteristics, inflammatory markers, cytokines, lymphocyte subsets, autoantibodies, and treatment regimens were analysed. Logistic regression and ROC analyses were performed to identify markers associated with pSS+RA overlap group. RESULTS: Compared with the non-RA group, patients in the overlap group had longer disease duration and higher ESR levels. IL-6, IL-17, and IL-8 levels were significantly elevated, accompanied by increased CD4+T-cell percentage and CD4/CD8 ratio, but decreased CD19+B-cell percentage. Anti-CCP and RF levels were markedly increased in the RA group. Biologic agents were used more frequently, whereas csDMARDs were used less frequently in the overlap group patients. Multivariable analyses identified IL-6, IgM, and CD19+B-cell percentage as independently associated with the overlap group. ROC analysis showed that anti-CCP had the highest discriminative ability (AUC = 0.873), while IL-6 demonstrated moderate diagnostic value (AUC = 0.71). CONCLUSION: Patients with pSS and concomitant RA exhibit an immune profile characterized by IL-6 pathway activation, T-cell predominance, and altered B-cell responses, closely resembling RA immunopathology. These findings provide insights into autoimmune overlap syndromes and support IL-6 as a potential therapeutic target in this population.