Two neutrophils among many red blood cells. Neutrophils are one type of cell affected by<unk> . Phagocytes (i.e. neutrophils and macrophages) require an enzyme to produce reactive oxygen species to destroy bacteria after they are ingested (phagocytosis), a process known as the respiratory burst. This enzyme is termed "phagocyte NADPH oxidase" (PHOX). This enzyme oxidizes NADPH and reduces molecular oxygen to produce superoxide anions, a reactive oxygen species. Superoxide is then disproportionated into peroxide and molecular oxygen by superoxide dismutase. Finally, peroxide is used by myeloperoxidase to oxidize chloride ions into hypochlorite (the active component of bleach), which is toxic to bacteria. Thus, NADPH oxidase is critical for phagocyte killing of bacteria through reactive oxygen species. (Two other mechanisms are used by phagocytes to kill bacteria: nitric oxide and proteases, but the loss of ROS-mediated killing alone is sufficient to cause<unk> .) Defects in one of the four essential subunits of phagocyte NADPH oxidase (PHOX) can all cause<unk>  of varying severity, dependent on the defect. There are over 410 known possible defects in the PHOX enzyme complex that can lead to<unk> .
Chronic granulomatous disease
Common variable immunodeficiency
Wiskott–Aldrich syndrome
Severe combined immunodeficiency
Primary immunodeficiency
X-linked agammaglobulinemia
Selective immunoglobulin A deficiency
SAPHO syndrome