Additionally, our GO enrichment analysis revealed that signaling was an integral component of biological processes in both RA and OA: 8 DEGs (KLRD1, ITGAX, CD79A, IRS2, JAK2, SEMA4D, ITGB7, and OLFM4) screened from the RA group and 8 DEGs (LBP, CDH2, HTR2B, TNFRSF11A, ADM, TLR7, IL1B, and DUSP2) screened from the OA group played significant roles in signaling biological processes. Here, HTR2B is linked to rheumatoid arthritis.