We recently provided evidence, as envisaged by several reports, that C1858T PTPN22 gene polymorphism which changes amino acid Arg (R) 620 to Trp (W) (R620W) in the encoded lymphoid tyrosine phosphatase protein (Lyp) (7, 13) could be a relevant target for immunomodulation in the treatment of patients affected by an autoimmune disease harboring the variant (7, 14). The gene discussed is PTPN22; the disease is autoimmune disease.