The PTPN22 gene is associated with idiopathic inflammatory myopathy

IntroductionThe aim of this study was to determine whether a single-nucleotide polymorphism (SNP; 1858CT, R620W) in the protein tyrosine phosphatase N22 (PTPN22) gene confers susceptibility to idiopathic inflammatory myopathy (IIM) in South Australian patients with IIM. Methods: Genotyping was performed on stored DNA from 199 patients with histologically confirmed polymyositis (PM), dermatomyositis (DM), and inclusion body myositis (IBM), and then compared with 455 matched controls. Associations with the 8.1 ancestral haplotype (AH), and myositis-specific (MSA) and myositis-associated (MAA) autoantibodies were investigated. Results: The PTPN22 R620W minor allele frequency was increased in IIM patients (50 of 398, 12.6%) compared with controls (75 of 910, 8.2%) (odds ratio 1.6, 95% confidence interval 1.1-2.3, P=0.016). In IIM patients, there was no association between the R620W minor allele and detection of any MSA/MAA (P=0.70), nor any evidence of epistasis with the 8.1 AH (P=0.69). Conclusions: The PTPN22 R620W minor allele is associated with susceptibility to IIM in SA patients, independent of the 8.1 AH. Muscle Nerve, 2016 Muscle Nerve55: 270-273, 2017