Utilization of PET in diagnosing adult-onset Still's disease: a systematic review

Adult-onset Still's disease (AOSD) is a rare systemic inflammatory disorder that frequently presents as fever of unknown origin (FUO), posing a diagnostic challenge. This study aimed to systematically review the diagnostic utility of 18 F-labeled fluorodeoxyglucose ( 18 F-FDG) PET/computed tomography (CT) in AOSD. A systematic review was conducted using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and registered in PROSPERO (CRD42023443831). Databases searched included PubMed, EMBASE, and Ovid up to December 2022. We included case reports, case series, cross-sectional, case-control, cohort studies, and clinical trials reporting PET/CT findings in adult patients diagnosed with AOSD. Data extraction included demographics, PET/CT findings, tracers used, standardized uptake values (SUVs), and diagnostic criteria applied. Data were analyzed following the SWiM framework because of heterogeneity. From 155 records, 54 studies (545 patients) were included. The majority were case reports or series ( n  = 40), with 14 observational studies or trials. 18 F-FDG was used in 85% of cases, predominantly for diagnostic purposes (77.7%). The most commonly used diagnostic criteria were Yamaguchi (63%). The highest maximum SUV (SUV max ) values were observed in the bone marrow (4.0 ± 1.4), spleen (4.0 ± 1.9), and liver (4.2 ± 2.1). PET/CT findings frequently revealed diffuse hypermetabolism in these organs, aiding in distinguishing AOSD from infectious or malignant etiologies. 18 F-FDG PET/CT appears to be a useful adjunct in the diagnostic workup of AOSD, especially in cases presenting as FUO. Typical uptake patterns in bone marrow, spleen, liver, and lymph nodes may support the diagnosis, though biopsy remains essential to exclude neoplastic mimics.