Subacute Thyroiditis Masquerading as Fever of Unknown Origin.

Subacute thyroiditis (SAT) is an inflammatory disease of the thyroid gland. It can present with overlapping features of other etiology of thyroiditis. It can present with thyroid enlargement and systemic symptoms such as fever as well as neck pain and may be confused with infectious thyroiditis. It can be difficult to diagnose and present as fever of unknown origin (FUO). A good history, physical examination, laboratory investigation, as well as imaging may aid in the correct diagnosis and prevent the inappropriate use of antibiotics. Treatment is usually with nonsteroidal anti-inflammatory drugs (NSAIDs) as well as corticosteroids. We herein present a case of SAT presenting as FUO. We highlighted the importance of proper clinical evaluation, the importance of thyroid imaging, and how to differentiate other forms of thyroiditis.