BTG3 and rheumatoid arthritis: In this study, we hypothesized the following: i) lncRNA CASC2/miR-18a-5p/BTG3 are abnormally expressed in the serum of RA patients; ii) lncRNA CASC2 regulates the progression of RA; and iii) the potential mechanisms of lncRNA CASC2 are associated with the miR-18a-5p/BTG3 signaling axis.