An Unexpected Mediastinal Fibrosis Case Detected and Evaluated of Treatment Response With 18F-FDG PET/CT.

IgG4-releated disease is systemic fibroinflammatory disease characterized by infiltration of IgG4-positive plasma cells in the affected tissue. Mediastinal fibrosis, which is also known as fibrosing mediastinitis, is a rare form of IgG4-releated disease. We present a case of mediastinal and retroperitoneal fibrosis in 52-year-old man who was detected with increased radiopharmaceutical uptake in 18F-FDG PET/CT imaging.