A 73-year-old male was found with lung nodule during a regular checkup. He had a history of asthma and hypertension for many years. Besides, he had undergone a nasal polypectomy before. Physical examinations showed that the right submandibular gland was swollen and hard. The laboratory tests indicated increased erythrocyte sedimentation rate (33 mm/h, 0-15 mm/h), IgG (22.49 g/L, 7-17 g/L), IgG4 (15600 mg/L, 80-1400 mg/L), T-IgE (6040 KU/L, 0-60 KU/L), and normal high-sensitive C-reactive protein (1.51 mg/L, 0-8 mg/L) level. Antinuclear antibody was positive (1:160, membrane pattern), while other autoantibodies were negative. A whole-body 18 F-fluorodeoxyglucose (18 F-FDG) positron emission tomography/CT (PET/CT) was performed (Fig. 1a) and revealed enlargement and diffusely elevated uptake of bilateral submandibular glands (especially right side), patchy 18 F-FDG-avid lesions in the prostate gland, a hypermetabolic nodule in the left lower lobe of the lung, and