Abstract: A 47-year-old man with treatment-naive sarcoidosis underwent 18F-FDG PET/CT. The image revealed clearly abnormal uptakes in his lymph nodes, muscles, and lungs, consistent with lesions of sarcoidosis. The patient had no symptoms and was under observation without treatment for sarcoidosis. At a 2-year follow-up, he underwent another 18F-FDG PET/CT scan, which revealed that several lesions with abnormal FDG uptake had significantly decreased, and some lesions had completely disappeared. Because sarcoidosis frequently shows spontaneous recovery, FDG uptake may show spontaneously dynamic changes in the associated lesions.