Immunoglobulin G4–Related Sclerosing Cholangitis Revealed by 68Ga-FAPI PET/MR

Abstract A 60-year-old woman with surgically confirmed immunoglobulin G4–related sclerosing cholangitis underwent 18 F-FDG PET/CT due to significantly elevated serum CA-19-9 level, which revealed a hypermetabolic lesion in the residual liver. 68 Ga-FAPI PET/MR was performed to further evaluate whether the FDG-avid lesion is a malignant tumor. Astonishingly, diffuse intense radioactivity was revealed throughout the liver, suggesting involvement of active immunoglobulin G4–related sclerosing cholangitis, but nonfocal elevated 68 Ga-FAPI accumulation in the FDG-avid lesion indicated postoperative change. From this case, we speculated that FAPI imaging could be used for evaluation of chronic liver disease because fibroblast activation protein has a profibrogenic role in chronic liver injury.