Background/Purpose: Imaging techniques in polymyalgia rheumatica (PMR) have revealed mainly bursitis, tenosynovitis, capsulitis and enthesitis. This is also the case for 18F-FDG-PET-CT. This technique, which has shown its interest for the diagnosis of PMR, allows an assessment of the metabolic activity of the entire musculoskeletal system and in particular of muscle structures.

The aim of this study was to evaluate muscle damage using 18F-FDG-PET-CT in PMR.

Methods: This is a retrospective study including patients with PMR (ACR/EULAR 2012 criteria) seen in our department, who had an 18F-FDG PET-CT examination between September 2012 and November 2018. A control group consisting of subjects without rheumatologic manifestations who had such an examination as part of neoplastic research or neoplastic disease control was also evaluated. PET evaluation included 17 sites suggestive of PMR, as previously reported [1], leading to a global PET score ranging from 0 to 51. Muscle hyper metabolism areas were similarly rated according to the same Goerres classification [2](0 = no uptake; 1 = slight uptake, less than liver; 2 = uptake like liver; 3 = uptake higher than liver). Muscle activity sites have been identified. A comparison of PMR patients with and without muscle involvement was performed using the Mann Whitney or Fisher’s exact test.

Results: 134 cases were reviewed, concerning 80 PMR (mean age 67.9) and 54 “controls” (mean age 68.1). Overall, PET muscle damage was observed in 27 cases (34%) in PMR and 6 cases (11%) in controls (p=0.004). The damage is bi or multi-focal in 16/27 cases. The affected muscular sites are: thighs and ischium-leg (n = 10), spinal (11), piriform/buttocks (7), pectoral (5), large serrated (4), subspinatus/subscapular (3), deltoid (1), trapezius (1). Fasciitis was found in 4 cases. As expected, PMR patients exhibited higher TEP scores than controls (p< 0.001). In PMR patients, PET muscle involvement was associated with higher ESR values (p< 0.05), but not with age, CRP or global PMR PET score.

Conclusion: Muscle involvement assessed by 18F-Fluorodeoxyglucose PET-CT is frequent in PMR (1/3 of cases), located at usual sites of symptoms of the disease, without association with age, CRP levels or global PET score for PMR. Muscle should be carefully evaluated during PET in cases of PMR; these pictures may be a new diagnosis feature of the disease.

References :

1 Sondag.M et al. Rheumatology 2016;55(8):1452-7.

2 Goerres GW, et al. Clin Nucl Med 2006;31:386-90.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/muscle-involvement-revealed-by-18f-pet-ct-in-polymyalgia-rheumatica/