Detection of CYBB Gene Expression by Reverse Transcription PCR as a Diagnostic Tool for X-linked Chronic Granulomatous Disease in Egyptian Children

Abstract

Primary immunodeficiency refers to a heterogeneous group of disorders characterized by poor or absent function in one or more components of the immune system which predisposes affected individuals to increased frequency and severity of infection. Chronic granulomatous disease is a genetic syndrome characterized by a dysfunction of the respiratory burst, which is necessary to kill certain phagocytosed pathogens. The fundamental defect in CGD lies in the NADPH oxidase, the enzyme complex responsible for initiating the respiratory burst. Defects in any of the six subunits of the NADPH oxidase enzyme can manifest as CGD. Thus, CGD patients can be phenotypically similar but genetically heterogeneous depending on which NADPH oxidase component is defective. By far the most common form of CGD is the X-linked recessive form. It results from a mutation of the CYBB gene encoding for gp91phox subunit of NADPH oxidase resulting in a greater number of affected males. However, there have been reports of affected females with the diagnosis of X-linked CGD attributed to skewed X chromosome inactivation.