A 10-year-old boy with a history of recurrent bacterial infections presents with fever and a productive cough. Biochemical analysis of his neutrophils demonstrates defective oxidative burst. This patient most likely has inherited mutations in the gene that encodes which of the following proteins?: (A) Catalase, (B) Cytochrome P450, (C) Myeloperoxidase, (D) NADPH oxidase
Answer is D. The impoance of oxygen-dependent mechanisms in the bacterial killing by phagocytic cells is exemplified in chronic granulomatous disease (CGD). Children with this disease suffer from a hereditary deficiency of NADPH oxidase which leads to decreased oxidative burst. Susceptible to recurrent bacterial infections. The most common variants are an X-linked defect in one of the membrane-bound components (gp91phox) and autosomal recessive defects in the genes encoding two of the cytoplasmic components (p47phox and p67phox). -Patients deficient in myeloperoxidase (choice C) cannot produce hypochlorous acid (HOCl) and experience an increased susceptibility to infections with the fungal pathogen Candida. -Catalase (choice A) conves hydrogen peroxide to water and molecular oxygen. Diagnosis: Chronic granulomatous disease