CGD is characterized by impaired production of reactive oxygen species and mutations in one of the following genes CYBB, CYBA, NCF1, NCF2, NCF4, CYBC1/EROS, which are the causes of the low levels of H2O2 production cells necessary for protection against mycobacterial infections (4, 15, 20). The gene discussed is CYBB; the disease is chronic granulomatous disease.