Here, we present a case of AST that could have been misdiagnosed and improperly treated as subacute thyroiditis. Both AST and subacute thyroiditis may present with painful thyroid swelling, fever, and leukocytosis following a URTI. In this case, atypical features for AST include the patient's age, presence of thyrotoxicosis, lack of dysphagia, dysphonia, and airway compromise, and marked clinical improvement within four days of admission . Thyrotoxicosis only occurs in 5–10% of patients with AST and is more often associated with subacute thyroiditis. Subacute thyroiditis, while far more common, is self-limiting; AST, while rare, can be life-threatening. Nevertheless, the patient had several risk factors for AST that increased clinical suspicion, allowing for an appropriate diagnostic workup and course of antibiotics to prevent complications. Misdiagnosis is particularly dangerous as administration of prednisone, used for subacute thyroiditis, may lead to deterioration of AST .