Diagnostic Value of 2-[(18)F]FDG PET/CT in a Patient with Atypical Subacute Thyroiditis: A Case Report

SIMPLE SUMMARY: Positron emission tomography/computed tomography (PET/CT) imaging with 2-deoxy-2-[(18)F]fluoro-d-glucose (2-[(18)F]FDG) could be a useful diagnostic tool to detect foci of infection or inflammation in patients with fever of unknown origin (FUO) or with inflammation of unknown origin (IUO). We report a case of a patient originally presenting with a clinical history of FUO and later with persistent high-sensitivity C-reactive protein (hsCRP) levels, even after antibiotic therapy. The patient underwent 2-[(18)F]FDG PET/CT to investigate and to localize a possible focus of infection or inflammation. Since only 2-[(18)F]FDG hotspots were detected in both thyroid lobes, specific thyroid diagnostic examinations were performed. Subacute thyroiditis (SAT) was then diagnosed, and other possible causes of FUO or IUO were excluded. We found it interesting to present this case to illustrate the potential diagnostic value of 2-[(18)F]FDG PET/CT imaging in patients with atypical SAT presenting only with FUO. ABSTRACT: Background: Positron emission tomography/computed tomography (PET/CT) imaging with 2-deoxy-2-[(18)F]fluoro-d-glucose (2-[(18)F]FDG) is a sensitive diagnostic imaging modality in oncology and could be a useful diagnostic tool in patients with fever of unknown origin (FUO) or with inflammation of unknown origin (IUO). Case presentation: We report a case of a patient originally presenting with a clinical history of FUO and later with persistent high-sensitivity C-reactive protein (hsCRP) levels, even after antibiotic therapy. The patient underwent 2-[(18)F]FDG PET/CT to investigate and to localize a possible focus of infection or inflammation. 2-[(18)F]FDG hotspots were detected in both thyroid lobes. Thyroid diagnostic examinations and follow up were performed. Subacute thyroiditis (SAT) was then diagnosed by thyroid examinations, and other possible causes of FUO or IUO were not found. Conclusion: This case illustrates the potential diagnostic value of 2-[(18)F]FDG PET/CT in patients with atypical SAT, who originally present with only a clinical history of FUO.