Hashimoto Thyroiditis (Autoimmune Thyroiditis; Chronic Lymphocytic Thyroiditis) By Glenn D Braunstein, MD, Cedars-Sinai Medical Center Reviewed / Revised Aug 2022 | Modified Sep 2022 View Patient Education Symptoms and Signs Diagnosis Treatment Key Points Hashimoto thyroiditis is chronic autoimmune inflammation of the thyroid with lymphocytic infiltration.