Autoimmune characteristics in Japanese children diagnosed with type 1 diabetes before 5 years of age

Background:  Several studies have shown that the autoimmune features in young children with type 1 diabetes differ from those in older pediatric patients as well as adults. The purpose of the present study was to examine the prevalence of β-cell autoantibodies, glutamic acid decarboxylase antibodies (GADA), and antibodies to the protein tyrosine phosphatase-related molecule IA-2 (IA-2A), at the time of diagnosis in Japanese children with type 1 diabetes who were younger than 5 years at diagnosis. Methods:  Subjects consisted of 23 Japanese children (nine boys, 14 girls), 3.1 ± 1.3 years of age at diagnosis (range, 1.1–4.8 years). The majority had severe metabolic decompensation accompanied by complete absence of β-cell function at diagnosis. We found 41.7% to have suffered viral infections before disease onset. Results:  The prevalence of antibodies to GAD and IA-2 at diagnosis in these subjects was significantly lower than those in older patients diagnosed after 5 years of age (31.6 % vs 86.3% and 47.1% vs 82.5%, P < 0.0001 and P = 0.0064, respectively). Among 17 patients in whom both antibodies were measured, only two (11.8%) had both GADA and IA-2A, three (17.6%) had GADA alone, six (35.3%) had IA-2A alone, and six (35.3%) had neither GADA nor IA2-A. Conclusions:  Non-autoimmune mechanisms or age-related differences in autoimmunity could be involved in the pathogenesis of diabetes in young patients.