PADI4 and ulcerative colitis: The specific reason underlying PAD dysregulation is not well defined, but there are many factors which may explain abnormal citrullination such as high levels of calcium that may affect PAD target specificity and their activity, unchecked translation of protein arginine deiminases that could cause an increase in citrullination [87], abnormal tumor necrosis factor alpha (TNF-α) signaling that is characteristic of ulcerative colitis (UC) and rheumatoid arthritis (RA), and TNF-α that can induce the translocation of PAD4 [88].