Consequently, we suggest that the differential expression of JUN, HLA-DRB4, STAT1, FOS, CD3D, HLA-DMA, MAPK8, HLA-DMB, LCK, HLA-DPB1, HLA-DRA, CD247, JAK2, HLA-DOB, HLA-DQA1, HLA-DPA1, involved in these pathways, might be a suitable marker to distinguish RA from OA. This evidence concerns the gene FOS and rheumatoid arthritis.