The tyrosine phosphatase non-receptor type 22 (PTPN22) SNP rs2476601 and the cytotoxic T-lymphocyte-associated protein 4 (CTLA4) SNP rs3087243 have also been shown to be associated with the risk of developing SLE and ME/CFS (17). Here, CTLA4 is linked to myalgic encephalomeyelitis/chronic fatigue syndrome.