Role of ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography in evaluation of immunoglobulin G4-related disease

Immunoglobulin G4-related disease (IgG4RD) is a multi-system disease complex with no specific etiology. The disease process is known to involve the exocrine glands, kidneys, lungs, lymph nodes, etc. Currently, role of conventional modalities in assessment of disease diagnosis, extent and severity is limited. ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) being a molecular/functional imaging technique has the potential to provide valuable information in this aspect. We retrospectively analyzed 10 previously untreated patients with clinical and biochemical suspicion of IgG4RD, who had undergone ¹⁸F-FDG PET/CT from November 1, 2016, to August 31, 2017. Analysis was done on the basis of qualitative and semi-quantitative parameters (maximum standardized uptake value (SUV_max )). Mean age of the 10 patients (M:F=1:1) was 37.1 ± 24.1 years. The most common presenting complaint was abdominal pain (5/10). Disease involvement of two or more sites was noted on ¹⁸F-FDG PET/ CT in all the patients. The disease spectrum on ¹⁸F-FDG PET/ CT included palatine tonsils (6/10, mean SUV_max 6.7), lymph nodes (5/10, SUV_max 7.1), salivary and lacrimal glands, lungs, bile ducts, kidneys, esophagus, pancreas, spleen, and retroperitoneum, in the decreasing order of frequency, which was consistent with the pattern, in literature. The maximum ¹⁸F-FDG uptake was noted in the axillary lymph nodes (SUV_max 11.9) and minimum in bile ducts (SUV_max 1.2). ¹⁸F-FDG PET/CT proved beneficial in the overall assessment of disease extent and severity in these patients and in providing a holistic picture which is not possible with the conventional diagnostic modalities. Thus, ¹⁸F-FDG PET/CT is a useful modality in the primary evaluation of patients with IgG4RD. (author)