G6PD and G6PD deficiency: In the most severe variants of G6PD deficiency, e.g., those leading to chronic non-spherocytic hemolytic anemia and chronic granulomatous disease (CGD), it was observed that leukocyte G6PD activity and PPP flux were markedly reduced (25, 26), leading to diminished oxidative burst and impaired bacterial killing in phagolysosomes (27).