Abstract: Background：Children with Munchausen syndrome characterized by factitious fever are often treated in other departments other than psychiatry and psychology. Doctors in these departments do not know enough about Munchausen syndrome. Therefore, it is difficult for children to get correct diagnosis and treatment timely, and the incidence rate may be underestimated. Objective：To summarize the clinical characteristics of children with Munchausen syndrome manifested as factitious fever , and to improve the understanding. Design：Case series report. Methods：Retrospective analysis was performed for consecutive hospitalized cases diagnosed with Munchausen syndrome presenting with factitious fever from January 2022 to January 2024 at nephrology, rheumatology and immunology departments of Children's Hospital of Jiangnan University, Children's Medical Center of Taihe Hospital Affiliated to Hubei Medical University, and the Rheumatology Department of Anhui Children's Hospital. Clinical data were collected from the management information system of each hospital, including gender, age at onset, disease course, medical history, characteristics of the fever, physical examination, and auxiliary examination. Main outcome measures：Characteristics of the fever. Results：Ten cases were included in this analysis, all of whom were girls with an onset age of 12 (10-14) years and a disease course of 6.3 (1-18) months. The average number of outpatient visits was 8 (4-12) times, the average number of hospitalizations was 3.5 (2-5) times, and the average number of hospitals visited was 3.5 (3-5). All had a history of repeated glucocorticoid and antibiotic treatments without efficacy. The body temperature of all patients rose to high fever (39.0-40.2°C) within a short period and returned to normal within about 5 minutes. Six cases occasionally experienced dizziness, including two with headaches and one with abdominal pain. There was no shivering or chills before the fever, and the timing was irregular. There was no sweating reaction when the temperature returned to normal. There were no changes in skin temperature, pulse, heart rate, or respiratory rate before and after the fever. Mental state and appetite were normal. Three cases had a slight increase in weight, while the others showed no decrease. No positive signs were found. Auxiliary examinations were all normal. Four cases were from single-parent families, five had long-term parental conflicts, and one was a left-behind child. All were referred to the psychology department for intervention, with a follow-up period of 8 (5-12) months. No similar fever episodes or other symptoms were observed during follow-up. Conclusion：Munchausen syndrome presenting with factitious fever is more common in female children/adolescents, often seeking treatment at multiple hospitals repeatedly. The body temperature can reach high fever within 3-8 minutes and return to normal in about 5 minutes. There are no typical pathophysiological changes during episodes, and laboratory and auxiliary examination results are normal. Despite a prolonged disease course, there are no changes in disease status.

Key words: Fever without source, Factitious diseases, Factitious fever, Sickness behavior, Children, Munchausen syndrome