Résumé : Introduction. — The recently identified role of a BRAF somatic mutation in the pathophysiologyof Langerhans cell histiocytosis (LCH) offers new therapeutic options. Herein we describe thecase of a 10-month-old infant with refractory high-risk LCH successfully treated with vemu-rafenib.Observation. — The patient first presented with cutaneous LCH at the age of 2 months. Thedisease remained undiagnosed until she was 6 months old, when it rapidly evolved to a multisys-temic high-risk and life-threatening disease, refractory to 2 lines of chemotherapy. BRAFV600Emutation was found at skin biopsy, and targeted therapy with vemurafenib was started whenshe was 10 months old. The treatment induced a fast and sustained response, but rapid relapseoccurred after treatment discontinuation, leading to resumption of treatment, once moreresulting in a sustained response.Conclusion. — Our case highlights the first-line role of dermatologists in establishing the diag-nosis of LCH, especially in children, in whom the eruption may be difficult to identify, leading todelayed diagnosis. Targeted therapy with vemurafenib has recently been described in children in this indication and our results support its efficacy, highlighting the need for prolonged treat-ment and raising the question of maintenance therapy, as well as the necessity for large-scaleand long-term studies.