A PREVIOUSLY healthy 15½-year-old boy with a 7-day history of intermittent fever with temperatures up to 38.5°C, anorexia, nausea, irritability, persistent migraine headaches, and a 9.5-kg weight loss was seen in the emergency department complaining of left lateral neck pain. No discrete masses were palpable, and the thyroid and overlying skin felt normal. On day 9 symptoms persisted, and the left thyroid lobe was enlarged (4-cm long) and firm. A clinical diagnosis of subacute thyroiditis was made, and nonsteroidal anti-inflammatory drugs (NSAIDs) were prescribed pending results of thyroid function tests. Two days later he returned with a further 2.7-kg weight loss, dysphagia, positional dyspnea, and marked fatigue. The left thyroid lobe was hard, tender, and 6.5-cm long. The isthmus and the right lobe felt normal, and there was no cervical lymphadenopathy. Tracheal compression was present on chest radiograph, and ultrasonography was performed (Figure 1). An inadequate sample was obtained for fine-needle aspiration; no purulent material was aspirated. Serum thyroxine levels from day 7 were markedly elevated at 97.9 pmol/L (reference range, 10-25 pmol/L), and TSH was incompletely suppressed at 0.03 mIU/L. Antimicrosomal antibodies were present at a titer of 1:1600 and thyroglobulin antibodies at 155.6 pmol/L (reference range, 0-32 pmol/L). Failure of response to NSAIDs led to the administration of a tapering course of prednisone. A barium esophagram was performed and demonstrated the cause of the problem (Figure 2).