Patients
A total of 139 consecutive pediatric patients with newly diagnosed LCH were admitted to our hospital between January 1, 2020, and June 30, 2021. One hundred and fourteen patients with available plasma samples were prospectively enrolled in the present study cohort. Twenty-five patients were excluded due to loss to follow-up after diagnosis (n = 18) or lack of plasma samples (n = 7). This study was approved by the Beijing Children’s Hospital Ethics Committee and was conducted in accordance with the Declaration of Helsinki. Informed consent was obtained from the guardians of the patients.