Characterizing IgG4-related disease with 18 F-FDG PET/CT: a prospective cohort study

Purpose IgG4-related disease (IgG4-RD) is an increasingly recognized clinicopathological disorder with immune-mediated inflammatory lesions mimicking malignancies. A cohort study was prospectively designed to investigate the value of 18 F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) in characterizing IgG4-RD. Methods Thirty-five patients diagnosed with IgG4-RD according to the consensus criteria were enrolled with informed consent. All patients underwent baseline 18 F-FDG PET/CT evaluation. Among them, 29 patients underwent a second 18 F-FDG PET/CT scan after 2 to 4 weeks of steroid-based therapy. Results All 35 patients were found with 18 F-FDG-avid hypermetabolic lesion(s); 97.1 % (34/35) of these patients showed multi-organ involvement. Among the 35 patients, 71.4 % (25/35) patients were found with more organ involvement on 18 F-FDG PET/CT than conventional evaluations including physical examination, ultrasonography, and computed tomography (CT). 18 F-FDG PET/CT demonstrated specific image characteristics and pattern of IgG4-RD, including diffusely elevated 18 F-FDG uptake in the pancreas and salivary glands, patchy lesions in the retroperitoneal region and vascular wall, and multi-organ involvement that cannot be interpreted as metastasis. Comprehensive understanding of all involvement aided the biopsy-site selection in seven patients and the recanalization of ureteral obstruction in five patients. After 2 to 4 weeks of steroid-based therapy at 40 mg to 50 mg prednisone per day, 72.4 % (21/29) of the patients showed complete remission, whereas the others exhibited > 81.8 % decrease in 18 F-FDG uptake. Conclusion F-FDG PET/CT is a useful tool for assessing organ involvement, monitoring therapeutic response, and guiding interventional treatment of IgG4-RD. The image pattern is suggested to be updated into the consensus diagnostic criteria for IgG4-RD.