FMO5 and chronic granulomatous disease: Chronic granulomatous disease (CGD) is a rare primary immunodeficiency (one in every 200,000-250,000 live births), caused by mutations in any of the five subunits of the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase complex. The host NADPH oxidase is essential in the first-line defense against pathogens.