To explore the clinical value of ¹⁸F-fluorodeoxyglucose (FDG) PET/CT in panniculitis presenting as fever of unknown origin (FUO).

Patients with FUO (n=503) who underwent ¹⁸F-FDG PET/CT examination in Peking University People′s Hospital between January 2013 and December 2019 were retrospectively analyzed, and those with final diagnosis of panniculitis were enrolled. The clinical and imaging data of patients with panniculitis were evaluated.

Five of the 503(0.99%) patients with FUO who underwent PET/CT imaging were diagnosed with panniculitis. Their age ranged from 41 to 76 years, and 3 of them were females. The main clinical manifestation was fever. Laboratory tests showed an increase in erythrocyte sedimentation rate and C-reactive protein. The ¹⁸F-FDG PET/CT imaging found localized FDG uptake foci in multiple adipose tissue, with maximum standardized uptake value (SUV_max) ranging from 0.8 to 5.0. Those lesions located in subcutaneous adipose tissue (n=3), mesenteric adipose tissue (n=3) and other adipose tissue in abdominal cavity and retro peritoneum (n=1). Diffusely increased FDG uptake of the spleen was found in 4 patients, diffusely increased FDG uptake of bone marrow was found in 3 patients, and multiple reactive hyperplasia lymph nodes was found in 2 patients. In addition, in 2 patients with the scanning field extended to the mid-thigh, high FDG uptake of the polyarticular synovium was also seen.

Panniculitis has some characteristics on ¹⁸F-FDG PET/CT imaging. ¹⁸F-FDG PET/CT is helpful for etiological diagnosis of FUO caused by panniculitis.

Panniculitis; Fever; Positron-emission tomography; Tomography, X-ray computed; Deoxyglucose