The associations were only found in ME/CFS patients, who reported an acute onset of disease with an infection (PTPN22 rs2476601: OR 1.63, CI 1.04–2.55, p = 0.016; CTLA4 rs3087243: OR 1.53, CI 1.17–2.03, p = 0.001), but not in ME/CFS patients without infection-triggered onset (PTPN22 rs2476601: OR 1.09, CI 0.56–2.14, p = 0.398; CTLA4 rs3087243: OR 0.89, CI 0.61–1.30, p = 0.268). This evidence concerns the gene PTPN22 and infection.