Clinical and FDG-PET/CT correlates in patients with polymyalgia rheumatica

Objective: We aimed to evaluate joint and vessel uptake in patients with polymyalgia rheumatica (PMR) by FDG-PET and correlate it with clinical findings. Methods: Consecutive PMR patients, without clinical signs of giant cell arteritis, underwent a standardised clinical examination and FDG-PET/CT. Controls were consecutive subjects undergoing FDG-PET for the suspicion of neoplasm not confirmed by the examination. Uptake was evaluated by a qualitative visual score, using the liver uptake as reference and by the semi-quantitative mean standardised uptake value (SUV) and target-to-background ratio (TBR) methods. Results: Eighty-four patients and 84 controls (55 women, median age 73 years, range 50-92 years in both groups) were studied. Sixteen patients were taking glucocorticoids (GC). PMR patients showed a higher articular uptake than controls. GC-treated patients showed uptake lower than GC-naïve patients, but still higher than controls. PMR patients showed a higher vascular uptake than controls in all districts except in the carotid arteries, when evaluated by the visual score. Conversely, the semi-quantitative approach yielded no significant differences. Forty-two patients (50%) showed PET evidence of large-vessel vasculitis (LVV), defined as uptake ≥ than that of the liver, and 11.9% showed LVV with vascular uptake higher than that of the liver. The correlation between clinical findings and uptake was scarce. Neither clinical nor laboratory findings could predict the presence of LVV. Conclusion: Patients with PMR show a typical joint pattern at FDG-PET. There are no clinical or laboratory predictors of LVV. Imaging appears to be the only tool to assess LVV in these patients. © Copyright Clinical and Experimental Rheumatology 2022.