In addition, mutations on diverse epigenetic regulators such as MLL3 (KMT2C), KDM6A, CREBBP (CBP), ARID1A and ARID1B have been observed in some HCL patients [14, 16], which may promote the disease progression by turning on oncogenic pathways and off tumor suppressive pathways via epigenetic modifications. The gene discussed is CREBBP; the disease is hairy cell leukemia.