Occult subacute thyroiditis mimicking classic giant cell arteritis.

We report the case of a 60-year-old man who presented with fever, weight loss, generalized aching, left temporal and ear pain, and an erythrocyte sedimentation rate of 125 mm/hour. Due to the presumed diagnosis of giant cell arteritis (GCA), the patient was treated with prednisone (60 mg daily), with immediate improvement in his symptoms. Biopsy of the temporal arteries revealed no significant inflammatory infiltrate. Further evaluation included assessments of thyroid function, which revealed an elevated T4 level, low thyroid-stimulating hormone level, and suppressed radioactive iodine uptake on thyroid scintigraphy. A diagnosis of subacute thyroiditis was made, prednisone therapy was tapered over 3 weeks, and treatment with beta blockers was instituted. The patient remained asymptomatic and returned to a euthyroid state. This case illustrates that subacute thyroiditis should be considered in the differential diagnosis of GCA.