PADI4 and rheumatoid arthritis: Interestingly, a specific PADI4 SNP haplotype has been reported to strongly induce apoptosis via multiple mitochondrial pathways through the downregulation of BCL-XL, upregulation of Bax, and the release of Cyt c into the cytoplasm; thereby providing a possible mechanism underlying the increase of SNP PADI4 activity and highlighting its critical role in the pathogenesis of RA (12).