Chronic Granulomatous Disease of Childhood: Clinical, Pathological, Biochemical, Molecular, and Genetic Aspects of the Disease

Abstract

The pathobiology of chronic granulomatous disease (CGD) of childhood, a heterogeneous phenotypic disorder characterized by chronic and recurrent infection, has become more completely understood over the past three decades. Blood neutrophils, monocytes, and eosinophils lack a respiratory burst required for effective killing of catalase positive bacteria by reduced by-products of oxygen. The disease is transmitted in at least two genetic forms: X-linked and autosomal recessive. In the X-linked form, a gene coding for a beta subunit protein required for cytochrome b presence on the plasma membrane of phagocytic cells is not expressed. The protein appears to be a constituent of the cytochrome b complex that requires an additional alpha subunit for complete expression. Cytochrome b is likely a component of leukocyte oxidase, which catalyzes the respiratory burst. The autosomal recessive form of the disorder appears to be controlled by a set of genes coding for soluble cofactors essential for oxidase expression. One or more of these cofactors have recently been shown to be deficient in several patients with autosomal recessive CGD. Optional therapy for CGD patients is presently not available. Long-term use of antibiotics may be helpful. The cloned product interferon gamma has been reported to improve superoxide generation, bactericidal activity, and immunoreactive cytochrome b in some CGD neutrophils and monocytes, both in vitro and in vivo. Currently a prospective clinical evaluation of the efficacy of interferon gamma is in progress. Molecular studies of expression and function of the X-CGD gene in phagocytic cells are in progress as well.

Key Words:

• chronic granulomatous disease
• cytochrome b
• leukocyte oxidase
• neutrophil