[18F]Fdg uptake in proximal muscles assessed by pet/ct reflects both global and local muscular inflammation and provides useful information in the management of patients with polymyositis/ dermatomyositis

Abstract

Objective: This study aimed to determine whether [18F]fluorodeoxyglucose-PET/CT ([18F]FDG-PET/CT) discriminates PM/DM from non-muscular diseases and also whether FDG uptake in proximal muscles reflects the activity and severity of muscular inflammation in PM/DM. Methods: Twenty treatment-naïve PM/DM patients who underwent [18F]FDG-PET/CT were retrospectively identified by reviewing medical records. The same number of age- and sex-matched control patients with non-muscular diseases were also identified. Standardized uptake value (SUV) was calculated for each of the seven proximal muscles. For patient-based assessment, mean proximal muscle SUV was calculated by averaging the SUVs for these proximal muscles bilaterally. Results: Mean proximal muscle SUVs were significantly greater in PM/DM patients than in control patients (median 1.05 vs 0.69, P<0.001). Mean proximal muscle SUVs significantly correlated with mean proximal manual muscle test scores (B=0.49, P= 0.028) and serum levels of creatine kinase (B=0.54, P=0.015) and aldolase (B = 0.64, P= 0.002). Furthermore, SUVs in proximal muscles from which biopsy specimens were obtained significantly correlated with histological grade for inflammatory cell infiltration (B=0.66, P= 0.002). Conclusion: Our results suggest that [18F]FDG-PET/CT is useful in the diagnosis of PM/DM when inflammation in proximal muscles is globally assessed with quantitative measurements. Our results also indicate that local FDG uptake in a proximal muscle reflects the activity of inflammation in the same muscle and provides useful information in determining the region for muscle biopsy. © The Author 2013. Published by Oxford University Press on behalf of the British Society for Rheumatology. All rights reserved.