A Case of Painful Hashimoto Thyroiditis that Mimicked Subacute Thyroiditis.

Hashimoto thyroiditis (HT) is an autoimmune thyroid disorder that usually presents as a diffuse, nontender goiter, whereas subacute thyroiditis (SAT) is an uncommon disease that is characterized by tender thyroid enlargement, transient thyrotoxicosis, and an elevated erythrocyte sedimentation rate (ESR). Very rarely, patients with HT can present with painful, tender goiter or fever, a mimic of SAT. We report a case of painful HT in a 68-year-old woman who presented with pain and tenderness in a chronic goiter. Her ESR was definitely elevated and her thyroid laboratory tests suggested subclinical hypothyroidism of autoimmune origin. (99m)Tc pertechnetate uptake was markedly decreased. Fine needle aspiration biopsy revealed reactive and polymorphous lymphoid cells and occasional epithelial cells with Hürthle cell changes. Her clinical symptoms showed a dramatic response to glucocorticoid treatment. She became hypothyroid finally and is now on levothyroxine therapy.