FDG uptake in intercostal muscles is an indicator of severe respiratory disease

A 40-year-old man with a history of pharyngeal wall cancer status postradiation therapy for 6 months underwent FDG-PET scan twice with in an interval of 5 months. The first PET images were normal. On the later PET images, incidental increased FDG uptake was noted in the intercostal muscles and in bilateral diaphragmatic crura. The patient had shortness of breath and a chest x-ray revealed marked biapical pleural thickening and scarring consistent with radiation fibrosis. This case demonstrates that FDG uptake in intercostal muscles in PET imaging can be an indicator of respiratory dysfunction and the use of accessory respiratory muscles.