CYBB and chronic granulomatous disease: X-linked CGD (X-CGD) results from mutations in the CYBB gene encoding the gp91phox subunit (about 70% of patients), while autosomal recessive (AR) CGD is associated with mutations in one of the CYBA, NCF1, NCF2, and NCF4 genes encoding for p22phox, p47phox, p67phox, and p40phox respectively.