The transmembrane catalytic subunit of NADPH oxidase Nox2 (gp91phox), responsible for the generation of large amounts of ROS catalytic subunit of NADPH oxidase, has been suggested to play a key role in mediating platelet ROS production and activation based on observations from the platelets of patients with chronic granulomatous disease, an X-linked disease related to mutations in the gene encoding Nox2 CYBB [50]. The gene discussed is FMO5; the disease is chronic granulomatous disease.