Introduction: IgG4-related diseases is an autoimmune disease newly recognized in recent years, it is rarely seen in clinical practice, the main clinical features of IgG4-RKD include acute or chronic renal insufficiency, proteinuria, elevated serum Ig G4, histopathological manifestations were tubulointerstitial nephritis, mainly characterized by a large amount of IgG4 positive plasma cell infiltration in the tubulointerstitial, it responded well to glucocorticoid therapy. Renal parenchymal damage could be seen on imaging. However, PET/CT imaging has been less reported, here we reported a case of IgG4-related kidney disease with PET/CT imaging.
Case presentation: A 50-year-old female presented with chills and fever for more than 2 months, she came to the urology department of our hospital for further diagnosis and treatment due to the right kidney occupation revealed by CT examination in local hospital. MRI plain scan plus diffusion imaging suggested multiple lesions in the right kidney, multiple nodular abnormally hypermetabolism foci in the right kidney were seen on PET/CT imaging, and the negative findings in the other parts of the body, therefore, a primary malignant tumor of the kidney was considered. Laboratory tests revealed elevated Levels of C-reactive protein, erythrocyte sedimentation rate, and IgG4 of immunoglobulin, histological pathology of right kidney puncture indicated inflammation and infection with surgical indications, she underwent radical right nephrectomy with laparoscopic under general anesthesia and was discharged 1 week after the right kidney operation, her clinical symptom disappeared and kept in good health during follow-up.
Conclusions: IgG4-related nephritis could manifest multiple or solitary hypermetabolism foci in unilateral kidney on PET/CT imaging, while the rest of the systemic PET/CT imaging manifestation was negative, which may be related to the infiltration of lymphocytes, plasma cells and inflammatory cells at the lesion site. The cause of abnormal accumulation of FDG in lesion site was unclear, and the true mechanism needs to be further clarified.