Compelling evidence support the relevance of NADPH oxidases in the enhanced ROS production that occurs in different types of leukemia such as AML (45), immunoresistant CML (67), chronic myelomonocytic leukemia (68), hairy cell leukemia (69), and adult T-cell leukemia induced by the human T-cell leukemia virus type 1 (70). The gene discussed is FMO5; the disease is leukemia.