The risk of ITP in population with homozygous GG genotype was 1.51 times higher than that in CC genotype [95%CI (1.11, 2.06), p = 0.009], indicating that the G allele at SNP1123 of PTPN22 may increase the susceptibility to ITP. This evidence concerns the gene PTPN22 and autoimmune thrombocytopenic purpura.