Background/Objectives: Fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) is a valuable imaging modality for detecting malignancies and diagnosing fever of unknown origin (FUO). However, data regarding FDG accumulation in bone marrow among pediatric acute leukemia (AL) cases are limited. In this study, we aimed to compare FDG-PET/CT findings between children with AL and those with inflammatory diseases (IDs), including FUO, and develop a scoring system for differential diagnoses. Methods: We retrospectively analyzed FDG-PET/CT findings in six children with AL and 22 with IDs. The maximum standardized uptake value (SUV max), visual score (VS), and spread score (SS) were evaluated across various bone marrow sites, including vertebrae, pelvic bone, humerus, forearm, and femur. Statistical analysis consisted of Mann–Whitney U test for group comparisons and receiver operating characteristic curve (ROC)/area under the curve (AUC) analyses to assess diagnostic performance. Results: SUV max, VS, and SS were significantly higher in children with AL across all evaluated sites. The combined VS + SS scoring system yielded the highest diagnostic accuracy. A simplified version using only the VS of the middle humerus and femur plus the SS showed comparable effectiveness. Conclusions: FDG-PET/CT in children with AL showed high FDG accumulation in bone marrow areas in the whole body. The simple scoring system, which comprises FDG accumulation in the middle portion of the extremities and the whole body, appears to be helpful in distinguishing AL from IDs in children. FDG-PET/CT-based visual scoring may provide supportive information alongside conventional diagnostics in pediatric acute leukemia.

Objective: This study aimed to investigate the clinical characteristics of pediatric-onset dystonia in Japan, addressing the diagnostic challenges arising from symptom variations and etiological diversity. Methods: From 2020 to 2022, questionnaires were distributed to 1218 board certified child neurologists (BCCNs) by Japanese Society of Child Neurology. In the primary survey, participants were asked to report the number of patients with pediatric-onset dystonia under their care. Subsequently, the follow-up secondary survey sought additional information on the clinical characteristics of these patients. Results: The primary survey obtained 550 responses (response rate: 45 %) from BCCNs for their 736 patients with dystonia. The predominant etiologies included inherited cases (with DYT10 being the most prevalent, followed by DYT5 and ATP1A3-related neurologic disorders), acquired cases (with perinatal abnormalities being the most common), and idiopathic cases. The secondary survey provided clinical insights into 308 cases from 82 BCCNs. Infancy-onset dystonia presented as persistent and generalized with diverse symptoms, primarily linked to ATP1A3-related neurologic disorders and other genetic disorders resembling acquired dystonia. Conversely, childhood/adolescent-onset dystonia showed paroxysmal, fluctuating courses, predominantly affecting limbs. The most common etiologies were DYT5 and DYT10 , leading to therapeutic diagnoses. Conclusion: Pediatric-onset dystonia in Japan was treated by 28 % of BCCNs. The majority of cases were inherited, with high prevalence rates of DYT5 and DYT10 . Infancy-onset dystonia exhibits diverse etiologies and symptoms, emphasizing the utility of various examinations, including genetic testing. These findings significantly contribute to our understanding of pediatric-onset dystonia in Japan, although this study has the limitation of questionnaire survey.