[¹⁸F]Fluorodeoxyglucose positron emission tomography/computed tomography for diagnosing polymyositis/dermatomyositis

[¹⁸F]fluorodeoxyglucose positron emission tomography/computed tomography ([¹⁸F]FDG-PET/CT) is useful for diagnosing cancers and inflammatory diseases. A polymyositis/dermatomyositis (PM/DM) lesion is an inflammatory heterogeneous disease of the striated muscle. In the present study, the maximum standardized uptake value (SUV_max) was compared between 22 cases with definite or probable PM/DM (PM/DM group) that underwent [¹⁸F]FDG-PET/CT examination and the same number of patients with no myopathy. The average proximal muscle FDG uptake value (SUV_average) for each patient was represented by calculating the average of the SUV_max for these muscles bilaterally. The correlation between creatine kinase (CK), serum creatine kinase isoenzyme, myodynamia of the proximal limb girdle muscle and SUV_max of each muscle group were analyzed. The results indicated that the SUV_max was markedly different between the PM/DM group and the non-myopathy group. It was demonstrated that [¹⁸F]FDG-PET/CT has a diagnostic value for PM/DM. The serum CK levels and the SUV_average were negatively correlated with myodynamia. [¹⁸F]FDG-PET/CT may be used for examination to assess the severity of myositis. Furthermore, it may provide detection sites for muscle biopsy in patients with myositis.