Incidental Adrenal Histoplasmosis Revealed by FAPI PET-CT in an Immunocompetent Patient

A 77-year-old male presented with pyrexia of unknown origin. Chest computed tomography (CT) showed adrenal lesions, a suspicion of neoplasia was raised, and Fluorodeoxyglucose Positron Emission Tomography (FDG PET-CT) was recommended. Since the patient had uncontrolled diabetes (Fasting Blood Sugar - 326 mg/dL), FDG-PET was not feasible. The patient, therefore, underwent Ga68-Fibroblast Activating Protein Inhibitor - 46 PET-CT (FAPI PET-CT). Scan showed high-grade Fibroblast Activating Protein (FAP) expression in bilateral enlarged adrenals. Findings appeared atypical for malignancy and the possibility of chronic inflammatory/infectious condition was raised. Biopsy proved adrenal histoplasmosis (AH). Although FDG avidity in AH is known and previously reported, this is best to our knowledge the first literature documentation of FAP expression in AH.