Chronic lymphocytic thyroiditis , also known as Hashimoto thyroiditis, is an autoimmune, inflammatory process that causes up to 55% to 65% of all euthyroid goiters, and almost all cases of thyroiditis in childhood and adolescence. A large North American prevalence study showed that as many as 1.2% of children aged 11 to18 years have chronic lymphocytic thyroiditis, as defined by an enlarged thyroid gland and detectable serum thyroid antibodies.