Hidden Valley Fever: A Case of Isolated Adrenal Coccidiodomycosis

Background Adrenalitis caused by Coccidioides species is a rare occurrence, and it is even more uncommon when there is no primary pulmonary involvement. Recognition of this is crucial in patients from endemic regions who present with indeterminate adrenal masses. Case Presentation A 75-year-old man from California's Central Valley was evaluated for a left adrenal incidentaloma with high attenuation, poor washout, and intense FDG uptake. Hormonal evaluation was unremarkable. Other serological workup for infectious causes was negative. A CT-guided biopsy demonstrated necrotizing granulomatous inflammation with fungal spherules consistent with Coccidioides. The patient was treated with fluconazole which resulted in an interval reduction in adrenal lesion size. Discussion This case highlights important diagnostic limitations of serologic testing in isolated extrapulmonary coccidioidomycosis. Imaging features may closely resemble adrenal malignancy, and biopsy is essential when serology is negative and imaging is indeterminate. Conclusion Adrenal coccidioidomycosis should be considered in the evaluation of adrenal masses in endemic regions. Tissue diagnosis is critical when noninvasive testing is inconclusive.