POS0822 NEW FACES OF POLYARTERITIS NODOSA: 18F-FLUORODEOXYGLUCOSE POSITRON EMISSION TOMOGRAPHY FINDINGS IN A SERIES OF 10 PATIENTS
Authors: C. Rousselin, T. Machet, G. Collet, T. Quéméneur, R. Ben Ticha, M. Verstraete, N. Le Gouellec, F. Demailly, A. Fagart
Journal: Annals of the Rheumatic Diseases (2021)

Background: 18 F-fluorodeoxyglucose positron emission tomography with computed tomography (FDG-PET/CT) is widely used in patients with large-vessel vasculitis (1). The benefits of FDG-PET/CT in polyarteritis nodosa (PAN) has only been assessed in a few case reports (2-3). Objectives: Our aim was to describe FDG-PET/CT findings in 10 patients with newly diagnosed PAN. Methods: This was a retrospective study of patients with PAN who underwent FDG-PET/CT at the time of diagnosis, between 2017 and 2020. The FDG-PET/CT data were analysed retrospectively and compared with clinical, biological, histological and conventional imaging data. Results: Ten patients were included: 9 men and 1 woman, median age of 67 (43–78) years. PAN was diagnosed according to ACR criteria (6) in 9 patients, and histologically in the remaining patient. The clinical manifestations were: systemic (n=10), muscular (n=6), joint (n=3), skin (n=3), peripheral nervous system (n=3), and gastrointestinal (n=2). All patients had high C-reactive protein levels (median, 223 mg/L). One patient had incomplete FDG-PET exploration. Three patients had begun corticosteroid therapy before their FDG-PET/CT scan. The main FDG-PET/CT abnormality was increased tracer uptake in the muscles, particularly in the connective tissue (perimysium, epimysium) (n=7), in linear (n=5) or focal (n=2) patterns. Increased FDG uptake in large-diameter vessels was observed in 4 patients, in the humeral (n=4), femoral (n=1) and the common interosseous (n=1) arteries. Nine patients had bone-marrow FDG uptake, six had splenic FDG uptake. Three patients had synovitis. Three had lymph-node uptake. One patient had subcutaneous FDG uptake, with a “leopard skin” appearance. Conclusion: FDG-PET/CT seems to be a useful non-invasive imaging technique for diagnosing PAN, particularly in patients with non-specific systemic features. Tracer uptake in muscular connective tissue seems to be a recurrent sign in patients with PAN. References: [1]Prieto-González S, Depetris M, García-Martínez A, Espígol-Frigolé G, Tavera-Bahillo I, Corbera-Bellata M et al. Positron emission tomography assessment of large vessel inflammation in patients with newly diagnosed, biopsy-proven giant cell arteritis: a prospective, case-control study. Ann Rheum Dis. 2014;73(7):1388-92. [2]Mino N, Yamashita H, Takahashi Y, Kaneko H. Polyarteritis Nodosa With Reversible FDG Accumulation in Vessels and Kidneys. Clin Nucl Med. 2019;44(11):889-891. [3]Schollhammer R, Schwartz P, Jullie ML, Pham-Ledard A, Mercie P, Fernandez P et al. 18F-FDG PET/CT Imaging of Popliteal Vasculitis Associated With Polyarteritis Nodosa. Clin Nucl Med. 2017;42(8):e385-e387. [4]Lightfoot RW Jr, Michel BA, Bloch DA, Hunder GG, Zvaifler NJ, McShane DJ et al. The American College of Rheumatology 1990 criteria for the classification of polyarteritis nodosa. Arthritis Rheum. 1990;33(8):1088-93. Disclosure of Interests: None declared