Bone Marrow Sarcoidosis with Pancytopenia and Renal Failure Presenting as Fever of Unknown Origin: The Pivotal Role of 18F-FDG PET/CT in Lesion Detection

We describe a case of fever of unknown origin (FUO), renal failure, and pancytopenia. Initially, lymph proliferative disorder was suspected; therefore, bone marrow biopsy and 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) were performed. Bronchoscopy and lung biopsy were performed because of abnormal FDG uptake in both lung fields. Imaging data and laboratory and histological results confirmed sarcoidosis with bone marrow invasion. The patient was discharged after favorable response to corticosteroid therapy. Sarcoidosis may present as FUO without typical specific presentations in the skin or lungs. Combined 18F-FDP PET/CT helped identify the biopsy site and confirmed the sarcoidosis diagnosis.