FDG PET/CT of Metabolic Myopathy With Posttreatment Follow-up

A 38-year-old woman presented with extreme fatigue and multiple lung nodules. She was referred for a PET/CT, which demonstrated multiple FDG-avid pulmonary nodules and lymph nodes with intense uptake within multiple muscle groups predominantly involving the paraspinal muscles and muscles of mastication. Histopathology of a paraspinal muscle biopsy revealed increased skeletal muscle lipid stores and increased mitochondria with normal morphology. This abnormality is seen in metabolic myopathy due to a disorder of fatty acid oxidation. Transbronchial biopsy showed no evidence of sarcoidosis. The patient was commenced on carnitine and riboflavin supplementation, and a follow-up PET/CT was performed.