The lack of association of anti-PAD2 antibodies with anti-CCP and anti-PAD3/4 antibodies, known serologies that associate with HLA-DRβ1 SE alleles (16, 17, 24, 25), suggested that anti-PAD2 may identify an immunogenetically distinct subset of RA patients. This evidence concerns the gene PADI2 and rheumatoid arthritis.