PADI4 and rheumatoid arthritis: An eQTL in the gene encoding PAD4 (PADI4, rs2240335-A) is associated with increased expression of PAD4 in neutrophils and is in almost complete linkage disequilibrium with the rs230188 SNP in PADI4 (LD r2 = 0.93) that confers an elevated risk of developing RA (185, 195).