ABSTRACT
Fever of unknown origin (FUO) is not infrequently a diagnostic dilemma for clinicians. Common infectious causes include endocarditis and abscesses in adults, and noninfectious causes include neoplasms and certain collagen vascular diseases. Endocrine causes of FUO are rare. The only endocrine disorder likely to present as FUO is subacute thyroiditis. Subacute thyroiditis usually occurs in middle-aged women as viral prodrome, neck tenderness, classic symptoms of thyrotoxicosis, and an elevated erythrocyte sedimentation rate. The patient may have abrupt onset of fever and chills with complaints of thyroid pain, or only low-grade fever with poorly characterized anterior neck pain. We present a case of FUO in a 48-year-old female who had had fever and neck pain for more than one month. Despite an extensive evaluation, the patient had persistent fever and no cause was found, with the exception of subacute thyroiditis. The fever resolved from the second day of treatment with low-dose steroid (prednisolone, 10 mg per day). This case illustrates that subacute thyroiditis should be considered in cases of FUO.