Muscle involvement on 18F-FDG PET-CT in polymyalgia rheumatica. A controlled retrospective study of 101 patients

18F-fluoro deoxy glucose PET scanner (18F-FDG-PET-CT) has shown its interest in the diagnosis ofpolymyalgia rheumatica (PMR) and makes possible to evaluate the metabolic activity of the entire musculoskeletal system and in particular muscular structures. The purpose of this study was to evaluatemuscle involvement using 18F-FDG-PET-CT in the case of PMR, compared to a non PMR population. Methods: This is a monocentric retrospective study of patients with PMR (ACR/EULAR 2012 criteria) whohad an 18F-FDG-PET-CT examination. A control group composed of subjects without rheumatologicalmanifestations who had such an examination as part of neoplastic research or follow-up of neoplastic diseases was also evaluated. The PET assessment included 17 sites suggesting a PMR, as previouslyreported. Areas of muscle hypermetabolism were classified in the same way according to the same semiquantitative classification. Muscle activity sites were identified. A comparison of patients with PMR withand without muscle damage was performed using the exact Mann-Whitney or Fisher test. Results: Two hundred and one cases were examined, involving 101 PMRs (mean age 68.6 years) and 100controls (mean age 67.7 years). Overall, PET muscle damage was observed in 34 cases (34%) in PMR and10 cases (10%) in controls (P = 0.004). Lesions are bi or multi-focal in half of the cases. The affected musclesites are: spinal muscles 19, scapular girdle 14, pelvic girdle 13, and thigh 6. Fasciitis was found in 3cases. In patients with PMR, PET muscle involvement was not associated with age, CRP or overall PMRPET score. Conclusion: Muscle damage assessed by 18F-Fluorodeoxyglucose PET-CT is common in PMR (1/3 of cases), located at the usual sites of disease symptoms, without association with age, CRP levels or the overallPET PMR score. The muscle must be carefully evaluated during a PET examination in cases of PMR. (c) 2020 Societe francaise de rhumatologie. Published by Elsevier Masson SAS. All rights reserved.