This hypothesis is supported by numbers of reports on genes that are associated with more than one autoimmune disease, for example the Protein Tyrosine Phosphatase Nonreceptor 22 (PTPN22) has been associated with T1D [19], RA [20], and SLE [21], the IRF5 with SLE [22], inflammatory bowel diseases [23], RA [24] and MS [9], the FCRL3 with RA, autoimmune thyroid disease, SLE [25] and MS [26], among several other examples. Here, PTPN22 is linked to rheumatoid arthritis.