Bilateral adrenal histoplasmosis incidentally detected on 18F-FDG PET/CT in an immunocompetent man with primary adrenal insufficiency: A case report.

Adrenal histoplasmosis is an uncommon manifestation of Histoplasma capsulatum infection and may closely mimic malignancy or granulomatous diseases on imaging. We describe an immunocompetent 51 year old man with 5 months of constitutional symptoms who underwent 18F-FDG PET/CT for evaluation of occult disease. The scan revealed intensely FDG avid bilateral adrenal masses with necrotic components, with no other abnormal sites. Biochemical testing confirmed primary adrenal insufficiency. CT guided adrenal biopsy, targeted to the most FDG-avid viable component, demonstrated necrotizing granulomatous inflammation with intracellular yeast forms consistent with Histoplasma capsulatum. Antifungal therapy with itraconazole plus glucocorticoid replacement led to clinical improvement and interval regression of adrenal lesions on follow-up. This case highlights the value of 18F-FDG PET/CT for detecting unsuspected adrenal histoplasmosis, localizing optimal biopsy targets, and facilitating timely treatment even in immunocompetent patients presenting with nonspecific symptoms.