CYBB and chronic granulomatous disease: Chronic granulomatous disease (CGD) is a genetic immunodeficiency caused by defects in any one of the five subunits of the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 2 (NOX2) complex including gp91phox (a.k.a Nox2) (CYBB (cytochrome b-245, beta polypeptide)), p47phox (NCF1 (neutrophil cytosolic factor 1)), p67phox (NCF2 (neutrophil cytosolic factor 2)), p22phox (CYBA (cytochrome b-245, alpha polypeptide)), and p40phox (NCF4 (neutrophil cytosolic factor 4)) [1].