Interestingly, the presence of the PTPN22C1858T SNP has no effect on the efficacy of anti-TNFα drug treatments used in RA (Potter et al., 2008), and studies examining its effect on efficacy of methotrexate have similarly shown mixed results without a convincing effect (Fedele et al., 2013; Majorczyk et al., 2020). Here, TNF is linked to rheumatoid arthritis.