HAPLN4 and rheumatoid arthritis: Among them, nine genes (FCGR3A, FCGR2A, TNFAIP3, CD40, FLT3, MFAP2, HAPLN4, FCRL3, and OLFML3) demonstrated expression levels that were associated with RA risk in consistent effect directions across different tissues, aligning with those observed in plasma protein levels.