Renal Involvement of Immunoglobulin G4-Related Disease Presenting as a Solitary Hypermetabolic Mass Mimicking Renal Tumor on 18 F-FDG PET/CT.

A 62-year-old woman with a 5-year history of diabetes insipidus was found with a solitary renal mass in contrast-enhanced CT. 18 F-FDG PET/CT showed a hypermetabolic mass in the right kidney. Besides, there was increased uptake in the pituitary stalk. The histopathological examination of renal biopsy confirmed the diagnosis of immunoglobulin G4-related disease. After treatment with prednisone and cyclophosphamide, there was obvious radiographic improvement of the renal lesion.