LCH-2011 regimen)was referenced,and the targeted drug Dabrafenib was added to treat those with the BRAF-V600E mutation.The clinical characteristics,BRAF-V600E mutation status,and treatment response between the single-system LCH(SS-LCH)group and the multisystem LCH(MS-LCH)group were summarized.Survival curves were plotted using the Kaplan-Meier method,and the Log-Rank test was used to compare the survival rates between the two groups.Results This study included a total of 31 cases,with 18 males and 13 females.The median age of onset was 10 months(ranging from 1 to 84 months).9 cases were SS-LCH,and 22 cases were MS-LCH,with 5 cases experiencing pituitary involvement/diabetes insipidus.Among the 27 cases that underwent BRAF-V600E mutation testing,20 were positive(3 cases in the SS-LCH group,with a positivity rate of 37.5%;17 cases in the MS-LCH group,with a positivity rate of 89.5%).The difference in the BRAF-V600E mutation positivity rate between the two groups was statistically significant(P = 0.011).The median follow-up time was 24 months(ranging from 3 to 62 months).The effective rate after 6 weeks of induction chemotherapy was 88.9%in the SS-LCH group(8/9)and 81.8%in the MS-LCH group(18/22).The observed progression-free rate at the end of the observation period reached 29.0%(9/31).All three deaths occurred in the MS-LCH group with involvement of high-risk organs.There was no statistically significant difference in the overall survival rate between the SS-LCH and MS-LCH groups,as well as between the BRAF-V600E mutation positive and negative groups(χ2 = 1.156,0.437;P = 0.282,0.508).Conclusion LCH in children is more common in infants and young children,with a high incidence of BRAF-V600E gene mutation in affected children,and is often seen in MS-LCH.Dabrafenib may help improve the prognosis of children with BRAF-V600E mutation.