The recent identification of somatic mutations in the Mitogen-Activated Protein Kinase (MAP-kinase) pathway gene, especially BRAFV600E in most tissue samples from adult histiocytoses [Langerhans cell histiocytosis (LCH) (2), Erdheim–Chester disease (ECD) (3), and Rosai–Dorfman disease (RDD) (4)], led to consider these diseases as myeloid neoplasm (5). Here, WNK2 is linked to Langerhans cell histiocytosis.