HLA-DR, HLA-DQB1 and PTPN22 gene polymorphism: association with age at onset for autoimmune diabetes

INTRODUCTION Autoimmune diabetes has different clinical manifestations related to the age at onset. It is divided into several subtypes, including "classical" type 1 diabetes (T1D) and latent autoimmune diabetes in adults (LADA). The LADA is considered a slowly progressing subtype of autoimmune diabetes, although the clinical picture is more similar to type 2 diabetes. MATERIAL AND METHODS The aim of this study is to investigate whether genetic predisposition influences age at onset in autoimmune diabetes. We studied rs2476601 PTPN22 gene polymorphism and HLA DR, HLA-DQB1 in 175 patients with classical type 1 diabetes, 80 LADA, and 151 control subjects from north-east Poland. RESULTS The frequencies of the PTPN22 TT genotype were higher in the group of patients with classical type 1 diabetes (6.3%) and LADA (11.3%) than in control subjects (0.7%) (p = 0.02 and p = 0007, respectively). In patients with classical type 1 diabetes we observed an increasing trend in frequencies of genotype TT dependent on age at onset (3.9% (0-5 year olds), 6.0% (6-15 year-olds), 8.2% (16-25 year olds), p = 0.048). The incidence of predisposing human leukocyte antigen (HLA) genotypes HLA DR3/DQB1*02 and DR4/DQB1*0302 was found to decrease in the group with type 1 diabetes in relation to age at onset and LADA (HLA DR3/DQB1*02 - 69.2% (0-5 year olds), 57.0% (6-15 year olds), 51.0% (16-25 year olds), 46.3% (LADA), p = 0.032; HLA DR4/DQB1*0302 - 80.8% (0-5 year olds), 63.0% (6-15 year olds), 51.0% (16-25 year olds), 43.8% (LADA), p = 0.0003), and to increase for the protective allele DQB1*0602 (0.0% (0-5 year olds), 1.0% (6-15 year olds), 2.0% (16-25 year olds), 6.3% (LADA), p = 0.029). CONCLUSIONS Thus, age at onset for autoimmune diabetes appears to be related to a combination of predisposing and protective HLA alleles. Against a background of HLA genetic predisposition, other non-HLA loci may influence age at onset for late autoimmune diabetes.