Younger age at onset of type 1 diabetes in concordant sibling pairs is associated with increased risk for autoimmune thyroid disease.

Individuals with type 1 diabetes are at increased risk for the development of additional autoimmune disorders compared with the general population (1–11). Autoimmune thyroiditis (AIT) and celiac disease are relatively common among patients with type 1 diabetes, with prevalence rates of 17 and 6%, respectively (4). We sought to examine the relationship between age at onset of type 1 diabetes and prevalence of additional autoimmune disorders in a sample of sibling pairs concordant for type 1 diabetes.