Bilateral orbital involvement of IgG4-related disease detected on 18F-Fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography

Rationale: IgG4-related disease (IgG4-RD) is a systemic immune-mediated fibro-inflammatory condition, which could involve multiple structures, including the pancreas, salivary glands, and lymph nodes. However, cases of IgG4-RD involving the bilateral orbits, salivary glands, submandibular glands, lymph nodes, and prostate are rare. Patient concerns: A 51-year-old man complaining of bilateral exophthalmos, reduced vision, and weight loss of 15 kg over 2 years presented to our department for evaluation. Diagnoses: Based on the elevated serum IgG4 level, postoperative pathology, and the features of 18 F-fluoro-2-deoxy-D-glucose ( 18 F-FDG) positron emission tomography/computed tomography (PET/CT), which revealed diffuse increased FDG uptake in many structures, he was diagnosed with IgG4-related disease involving the bilateral orbits, salivary glands, submandibular glands, lymph nodes, and prostate. Interventions: Because of the significant bilateral proptosis and exposure keratoconjunctivitis in the right eye, bilateral soft-tissue masses located in the orbits were resected, and the patient was started on oral methylprednisolone with gradual tapering. Outcomes: The patient's symptoms gradually relieved after the operation and glucocorticoid therapy. Four months later, cranial axial CT revealed remarkable narrowing of soft-tissue masses in the bilateral orbits, and his serum IgG4 level reduced sharply. Lessons: IgG4-RD should be considered in cases of diffuse FDG uptake in the bilateral orbits, salivary glands, submandibular glands, lymph nodes, and prostate on PET/CT.