Multisystem FDG-avid lesions mimicking malignancy in a teenager with hyper-IgE syndrome: A case study with literature...

Hyper-IgE Syndrome (HIES) is a rare immunodeficiency predisposing patients to infections, inflammation, and occasional neoplasia. We report a 17-year-old boy with HIES who presented with severe right thigh pain. FDG-PET/CT demonstrated a right adrenal mass (SUV_max=5.4), multiple pulmonary nodules, and a lytic-sclerotic femoral lesion (SUV_max=4.6), initially suggesting disseminated malignancy. Biopsy confirmed acute osteomyelitis and a benign spindle cell tumor of the adrenal gland. Two months later, persistent fever and elevated ESR prompted re-evaluation, revealing intense FDG uptake in the thoracic aorta (SUV_max=20.5) consistent with large vessel vasculitis, later confirmed by angiography. The combination of infection, benign tumor, and vasculitis illustrates the broad FDG uptake spectrum in HIES and the risk of misdiagnosis as malignancy. Integration of clinical, imaging, and histopathologic data was critical for accurate diagnosis. This case highlights FDG-PET/CT's value in detecting inflammatory vascular disease and monitoring therapy, while reinforcing the importance of biopsy for definitive diagnosis. In immunodeficient patients, a multimodal diagnostic approach is essential to distinguish between malignant and benign FDG-avid lesions.