18F-Fluorodeoxyglucose positron emission tomography for the assessment of myositis: a case series

To establish whether 18FFluorodeoxyglucose (FDG) positron emission computerised tomography (FDG-PET/CT) might reveal active disease in patients with myositis.

We studied 12 patients with active myositis (2 polymyositis, 10 dermatomyositis). The controls consisted of 14 randomly chosen subjects without muscle disease. FDG uptake was expressed as the ratio of maximum proximal muscle to liver standardised uptake value. Magnetic resonance of the thigh and pelvic floor muscles was performed on a 1.0 or 1.5T scanner using a surface coil. Oedema (1= present, 0=absent) was assessed by fat suppressed sequences in 17 muscles and a score (0-17) calculated by adding the separate scores. Muscle strength was evaluated in 12 muscle groups by manual muscle test and graded according to the extended Medical Research Council scale (0-5).

FDG uptake in proximal muscles was significantly higher in patients with myositis (median 0.58, interquartile range 0.52) than in those without (median 0.30, interquartile range 0.09; p<0.001 Mann-Whitney U-test). FDG muscle uptake in patients with myositis did not correlate with disease duration, creatine kinase levels, muscle strength, or magnetic resonance scores.

FDG-PET/CT can reveal FDG uptake by affected muscles of patients with myositis and might potentially be useful to assess myositis activity.