The tryptophan 620 allele of the lymphoid tyrosine phosphatase (PTPN22) gene predisposes to autoimmune Addison's disease

Previous studies of the association between autoimmune Addison's disease (AAD) and a nonsynonymous single nucleotide polymorphism (SNP) in the PTPN22 gene (C1858T, pR620W; SNP ID no. rs2476601) have shown conflicting results. We aimed to examine this association using additional cohorts of AAD subjects from the UK and Poland. DNA samples were obtained from UK and Polish AAD subjects (n = 251 and 87, respectively) and ethnically matched healthy controls (n = 429 and 236, respectively). Genotyping for the C1858T PTPN22 marker was performed by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) assay. Meta-analysis of the results, together with those from three other populations, was performed using RevMan v5.0 software. In 251 UK AAD subjects the frequency of the PTPN22 1858T allele was 12.2% compared to 7.8% in healthy UK controls; P = 0.008. Similarly, in 87 Polish AAD subjects the PTPN22 1858T allele was found in 19.5% of alleles compared to 11.7% in healthy Polish subjects; P = 0.010. A meta-analysis, combining these result with published data for three other populations, involving 797 AAD subjects and 2032 controls in total, showed that the 1858T allele was associated with AAD susceptibility with a pooled odds ratio (OR) of 1.44 [95% confidence interval (CI) 1.21-1.72; P = 5.6 x 10(-5)], under a fixed-effects model. This study confirms the association between the PTPN22 1858T allele and AAD in an expanded UK cohort and in the previously unstudied Polish population. This meta-analysis allows for the first time a reliable estimate of the strength of effect of this autoimmune disease susceptibility allele across different European Caucasian populations.