NCF4 and chronic granulomatous disease: CGD is caused by mutation in any one of the five subunits of the NADPH oxidase, including gp91phox (cytochrome b-245, β-polypeptide, CYBB), p22phox (cytochrome b-245, α-polypeptide, CYBA), p47phox (neutrophil cytosolic factor 1, NCF1), p67phox (NCF2), and p40phox (NCF4).