This is an open-label study to investigate the diagnostic performance of 18F-FDG PET/CT (positron emission tomography/computed tomography) in evaluation of patients with IgG4-related disease. A single dose of 18F-FDG will be intravenously injected into patients with IgG4-related disease before and after treatment.

Immunoglobulin G4-related disease (IgG4-RD) is a recently defined emerging clinical entity characterized by tissue infiltration by IgG4-positive plasma cells, tissue fibrosclerosis and elevated serum IgG4 concentration. The most important feature of IgG4-RD is chronic inflammation with multiple organ involvement. However, some organ involvements are difficult to find by ultrasound, CT or MRI.

18F-FDG PET/CT is a sensitive imaging tool for inflammation. In this study, PET/CT were performed in patients with IgG4-RD both before and after glucocorticoid treatment by a single dose of 18F-FDG. Visual and semiquantitative method will be employed to assess the PET/CT images. The PET/CT image data will be used to establish a diagnostic model as well as assessment criteria for response evaluation of IgG4-RD treatments.

Inclusion Criteria:

• Males and females

• Age 18-75 years old with informed consent

• Patients with IgG4-RD:

  1. swelling, sclerosing and inflammatory involvement of one or more organ, including sclerosing pancreatitis, sclerosing cholangitis, inflammatory pseudotumors, retroperitoneal or mediastinal fibrosis, interstitial nephritis, hypophysitis, sclerosing dacryoadenitis, sialadenitis, inflammatory aortic aneurysm, lymphadenopathy, or other inflammatory conditions;
  2. elevated serum IgG4 (>1.35 g/L) or with histopathologic features of fibrosis and/or lymphocytic and polyclonal plasma cell infiltration (and IgG4+ plasma cells on immunohistology when performed);
  3. exclusion of other diseases.

Exclusion Criteria:

• Females planning to bear a child recently or with childbearing potential;
• Inability to complete the examination;
• Concurrent severe and/or uncontrolled and/or unstable diseases;
• Currently under treatment using glucocorticoids.