NCF2 and chronic granulomatous disease: Mutations within the X-linked gp91 phox gene (CYBB) cause the X-linked form of CGD, while the autosomal recessive forms of CGD are due to mutations in in CYBA, NCF1, NCF2, or NCF4 which encode for p22 phox, p47 phox, p67 phox, and p40 phox, respectively (10).