Characterizing IgG4-RD With 68Ga-FAPI PET/CT

Immunoglobulin G4-related disease (IgG4-RD) is an immune-mediated fibroinflammatory condition that is capable of affecting multiple organs. Common forms of presentation include:Type 1 (IgG4-related) autoimmune pancreatitis (AIP)，IgG4-related sclerosing cholangitis, major salivary gland enlargement or sclerosing sialadenitis; Orbital disease, often with proptosis and retroperitoneal fibrosis. The involved organs share a number of core pathologic features and striking clinical and serologic similarities, including tumor-like swelling of involved organs, a lymphoplasmacytic infiltrate enriched in IgG4-positive plasma cells, and a variable degree of fibrosis that has a characteristic "storiform" pattern. 68Ga-FAPI has been developed as a tumor-targeting agent as fibroblast activation protein is overexpressed in cancer-associated fibroblasts and it might be a pan-tumor PET agent. Recently we have reported a case of IgG4-related disease revealed by 68Ga-FAPI and 18F-FDG PET/CT which showed FAPI was not more tumor-specific than FDG, furthermore,it might be more sensitive than FDG in detecting a certain type of inflammations-like the pancreatic lesion. Thus this prospective study is going to investigate whether 68Ga-FAPI PET/CT may be superior for diagnosis, therapy response assessment and follow-up of IgG4-related disease.