In addition, the relationship can be assumed between the methotrexate efficacy and the polymorphic variants of other genes encoding proteins, presumably playing an important role in the JIA pathogenesis, including interleukin 2 receptor subunit alpha (IL2Rα), lymphotoxin alpha (LTα), macrophage migration inhibitory factor (MIF), protein tyrosine phosphatase nonreceptor type 22 (PTPN22), peptidyl arginine deiminase 4 (PADI4) [17–19]. This evidence concerns the gene PTPN22 and juvenile idiopathic arthritis.