SAT0522 Vascular and joint inflammation are negatively correlated in patients with polymyalgia rheumatica, giant cell arteritis and fever of unknown origin

Background 18 F-Fluorodeoxyglucose positron emission tomography (PET) reveals the presence of large vessel vasculitis (LVV) in 30%–40% of patients with apparently isolated polymyalgia rheumatica (PMR), in 70%–80% of patient with giant cell arteritis [1] and in about 20% of patient with fever of unknown origin (FUO) [2] , suggesting that these conditions may be different clinical manifestations of the same entity. Objectives To evaluate and compare the patterns of vascular and joint uptake in patients with PMR, GCA, and FUO. Methods Consecutive patients with a diagnosis of PMR, GCA or FUO underwent a thorough clinical examination and a PET/CT scan. Arterial and joint uptake of FDG were scored relative to liver uptake with a 4-point scale. The values of each district examined were summed to obtain a total vascular score (TVS) and a total joint score (TJS). A semi-quantitative analysis of FDG uptake was carried out. Arterial FDG uptake was quantified by calculating the mean standardised uptake value (SUV) within each region of interest (ROI) and the results expressed as the ratio between mean SUV value of each ROI and the blood-bool (SUV/BP). To assess joint metabolism, CT-based ROIs were bilaterally drawn on joint and bursal spaces. Results One hundred and thirty-one patients were included, 89 females and 42 males, with a median age of 74 years (range 47–92). Ninety-seven patients were diagnosed as PMR, 13 as GCA, 16 with both PMR and GCA and 5 patients presented with FUO. FUO patients showed a higher mean arterial SUV in comparison to PMR (0.77 vs. 1.15, p=0.004) and GCA patients (0.81 vs 1.15, p=0.052). Similar and more striking results were obtained using visual scoring. FUO patients showed always increased uptake in the large vessels. PMR patients showed statistically lower TVS than GCA +PMR, GCA and FUO patients. Patients with PMR showed a statistically significant higher mean joint SUV than GCA patients (p=0.01). The highest mean articular uptake was shown by PMR patients and the lowest by FUO patients. Mean TJS of PMR patients was significantly higher than that of GCA and FUO patients (p Conclusions Although patients with diseases different from PMR were few, our PET/CT study support the view that there is a continuum in the intensity of inflammation, with FUO >GCA>PMR+GCA> PMR for vessels, and the opposite for joints. Vascular and joint inflammation were negatively correlated. Our data support the view that similarities exceed differences in these conditions, with clinical features depending from the relative contribution of vessel and joint involvement. References [1] Puppo C, Massollo M, Paparo F, Camellino D, et al. Giant Cell Arteritis: A Systematic Review of the Qualitative and Semiquantitative Methods to Assess Vasculitis with 18 F-Fluorodeoxyglucose Positron Emission Tomography. Biomed Res Int2014;2014:574248. [2] Schonau V, Vogel K, Englbrecht M, et al. The value of 18 F-FDG-PET/CT in identifying the cause of fever of unknown origin (FUO) and inflammation of unknown origin (IUO): data from a prospective study. Ann Rheum Dis2018;77(1):70–7. Disclosure of Interest None declared