In the 2016 Histiocyte Society classification [4], LCH was reclassified as clonal inflammatory myeloid neoplasm harboring genetic alterations leading to aberrant oncological signaling [5, 6], with BRAF V600E and MAP2K1 gain-of-function mutations found in more than 70% of LCH patients [7]. Here, MAP2K1 is linked to Langerhans cell histiocytosis.