Langerhans cell histiocytosis (LCH) is a myeloproliferative neoplasm of pathologic dendritic cells (DC). This is supported by the clonality of these cells, the recurrent mutations in BRAF-V600E and other MAPK pathway genes, the identification of the BRAF-V600E mutation in hematopoietic stem cells and myeloid precursors in patients with high-risk LCH[1]. An estimated 4-5 per million patients are affected each year, from the neonatal period to adulthood, although it appears to be more common in children of 0-15 years[2,3]. [...]