CA4 and rheumatoid arthritis: There were 19 key DEGs found commonly shared in both the RA and the T2D groups associated with these shared bio-functions: ARG1↑, BPI↑, CA1↑, CYP4F3↑, DEFA4↑, DEFA1↑, HLA-DQA2↑, LTF↑, MMP8↑, MMP9↑, MPO↑, SELENBP1↑, BPI↑, CD177↑, ITGB4↓, SNAI1↓, MT2A↑, BMX↑, CA4↑.