Background IgG4-related disease (IgG4-RD) is a relatively common and clinically important disease. It is very difficult to confirm the diagnosis due to the ubiquity of its lesions, which can involve the pancreas, salivary glands, retroperitoneum, and kidney. An elevated serum IgG4 level is not diagnostic of the disease. In 2011, comprehensive diagnostic criteria for IgG4-RD were established. These criteria require histopathology to confirm the diagnosis, as well as to exclude malignancy or other similar diseases. However, the diagnostic rate is low due to difficulty in determining the site to be biopsied.
Objectives FDG-PET/CT is a non-invasive imaging technique commonly used in clinical oncology. 18 F-FDG accumulation is recognized as useful for diagnosing and monitoring the response to therapy in patients with some inflammatory disorders. We investigated the utility of FDG-PET/CT to determine the diagnosis in patients suspected of having IgG4-RD.
Methods We studied 36 patients with suspected IgG4-RD in our facility between Jan. 2008 and Dec. 2013. We retrospectively studied the relation of serum IgG4 levels, pattern of FDG uptake, maximum standardized uptake value (SUVmax), pathological findings, and clinical course.
Results We diagnosed 27 patients with IgG4-RD or other diseases. There were nine cases in which FDG-PET/CT was the only modality indicating a disease site for biopsy. Other diagnoses included lymphoma, Castleman's disease, and tuberculosis. There was no correlation between serum IgG4 and SUVmax, but there was a correlation between SUVmax and histopathological findings.
Conclusions FDG-PET/CT is useful in selecting a biopsy site for the pathological examination of tissue that is necessary to diagnose or exclude IgG4-RD. Its regular use has the potential to improve the diagnostic rate of this entity.
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Disclosure of Interest None declared