Recurrent Immunoglobulin G4-Related Disease Shown on 18F-FDG and 68Ga-FAPI PET/CT.

A 21-year-old man had been diagnosed with immunoglobulin G4-related disease (IgG4-RD) for 5 years, and the disease recurred 1 month ago. F-FDG PET/CT revealed intense FDG activity in the pituitary stalk, submandibular gland, pleura, pericardium, pancreas, liver, prostate, and multiple lymph nodes, which were considered the involvements of IgG4-RD. Ga-FAPI PET/CT also showed intense Ga-FAPI uptake in the above FDG-avid lesions except the lymph node involvement. Additionally, involvement in the lacrimal glands was detected by Ga-FAPI. The positive findings of Ga-FAPI in the current case highlighted that Ga-FAPI may have value in the evaluation of IgG4-RD.