Langerhans cell histiocytosis (LCH) is a disease originating from abnormal proliferation of CD1a+/CD207+ myeloid dendritic cells and characterized by activation of the mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) signaling pathway [1, 2]. The gene discussed is CD1A; the disease is Langerhans cell histiocytosis.