The Roles of Anti-RNP Antibodies in Primary Sjögren’s Syndrome Pathogenesis and Severity May Be Underestimated

Abstract Background Associations between anti-ribonucleoprotein (RNP) antibodies status and distinct clinical primary Sjögren’s syndrome (pSS) subtypes have not yet been firmly established. The aim of our study i s to determine whether associations exist between RNP antibody status and the clinical manifestations, laboratory features, or disease activity in pSS. Methods A retrospective cohort of 39 anti-RNP antibody-positive and 294 anti-RNP antibody-negative pSS patients was assembled. Data regarding demographic information, glandular and extraglandular manifestations, laboratory findings, and disease activity (scored according to the European League Against Rheumatism SS disease activity index (ESSDAI)) were extracted from patient records. Univariate methods followed by multivariable logistic regression analysis were used to evaluate potential associations between anti-RNP antibody status and clinicopathologic features. Results Patients with anti-RNP antibody-positive pSS had a higher prevalence of Raynaud’s phenomenon (RP) and hematological, pulmonary, lymphatic system, and mucocutaneous involvement; higher erythrocyte sedimentation rates and serum IgG levels; lower lymphocytes counts; and significantly higher ESSDAI scores (median (interquartile range): 13 (7–18) versus 7 (3–12), p < 0.001). No significant differences were observed between groups for C-reactive protein levels and rheumatoid factor or anti-Ro/SSA or -La/SSB antibody positivity. Multivariate analysis identified RP, interstitial lung disease (ILD), and lymphatic system involvement as independent predictors of anti-RNP antibody positivity in pSS patients. Conclusions In this cohort, anti-RNP antibodies were associated with several clinicopathologic features of severe pSS, such as RP and hematologic, lymphatic, and pulmonary disorders. Therefore, anti-RNP antibodies may play an important role in the pathogenesis and severity of pSS.