aureus, followed by various Gram-negative organisms, including B. cepacia complex and Serratia marcescens. Recurrent impetigo, frequently in the perinasal area and caused by see more S. aureus, usually requires prolonged courses of oral and topical antibiotics to clear. Hepatic (and perihepatic) abscesses are also quite common in CGD and are caused typically by S. aureus. Patients usually present with fever, malaise and weight loss. Osteomyelitis is another important infection in CGD and can arise from haematogenous spread of organisms

(S. aureus, Salmonella spp., S. marcescens) or contiguous invasion of bone, seen typically with non-A. fumigatus pneumonia, such as A. nidulans spreading to the ribs or vertebral bodies. Perirectal abscesses are also common in CGD patients, and once formed can persist for years despite aggressive anti-microbial therapy and fastidious local care. Other frequently encountered catalase-positive microbial agents are Escherichia coli species, Listeria species, Klebsiella species, Nocardia and Candida species. CGD patients usually manifest their symptoms at an early age, in the first 2 years of life. However, due to the diverse genetic causes of the disease (see below), some patients may also present later in life. Most CGD patients (about 80%) are male, because the main cause of the disease is a mutation in an X-chromosome-linked learn more gene. However, defects in autosomal genes may also underlie the disease and cause

CGD in both males and females. CGD is caused by the failure of the patients’ phagocytic leucocytes to kill a wide variety of pathogens. This is due to a defect in these phagocytes in producing reactive oxygen species (ROS), which are needed for the killing process. In normal phagocytes, these ROS are generated by an enzyme called

nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. This enzyme is composed of five subunits, two of which are in resting cells localized in the plasma membrane and three in the cytosol. The two membrane-bound subunits are a transmembrane glycoprotein (gp) with a molecular mass of 91 kD, called gp91phox (phox for phagocyte oxidase) and another transmembrane protein with a molecular mass of 22 kD, called p22phox. These Protirelin two proteins form a heterodimer and are dependent upon each other’s presence for maturation and stable expression. This heterodimer is called cytochrome b558 because gp91phox contains two haem groups with an absorbance peak at 558 nm. The three cytosolic subunits (p40phox, p47phox and p67phox) form a heterotrimer that translocates to cytochrome b558 upon cell activation (e.g. by binding of micro-organisms or chemotactic factors to membrane receptors). As a result, the conformation of gp91phox is slightly changed, which enables NADPH in the cytosol to bind and donate electrons to this protein. These electrons are then transported within gp91phox to molecular oxygen on the apical side of the membrane.