WNK2 and Langerhans cell histiocytosis: Historically, LCH has been subdivided into four syndromes (Letterer-Siwe, Hand-Schuller-Christian, eosinophilic granuloma, and Hashimoto-Pritzker); however, current evidence indicates that not all cases fit into these categories.1, 2 Recently, LCH has been redefined as an inflammatory myeloid neoplasia, attributed to the activation of mutations in the mitogen-activated protein kinase (MAPK) pathway,2 with the BRAF-V600E gene mutation being the most prevalent one.3