PADI4 was expressed in myeloid lineage cells and rheumatoid arthritis synovial tissues [48], as well as in Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans in gingival tissue [49], and it post-translationally converts peptide-bound arginine residues into citrulline, leading to citrullinated epitope generation, which is recognized by ACPAs [50]. The gene discussed is PADI4; the disease is rheumatoid arthritis.