PTPN22 and type 1 diabetes mellitus: Proportion of carriers of at least one polymorphic PTPN22 rs2476601allele in subjects with coexisting T1D and CD was significantly lower compared to T1D (OR = 0.41, 95% CI = 0.19–0.85, P = 0.016) and the difference remained significant after adjustment for age at diagnosis, gender and HLA genotype (OR = 0.36, 95% CI = 0.17–0.78, P = 0.010).