On the other hand, the influence of genetic factors on the modulation of the expression and function of PADs has been proven (8), and, even though the role of single-nucleotide polymorphisms (SNPs) and of a functional haplotype in PADI4 has been established, few studies that have determined the role of SNPs in PADI2 in the genetic susceptibility to RA or its association with the serologic status and the clinical parameters that are related to the disease. This evidence concerns the gene PADI4 and rheumatoid arthritis.