Although G6PD deficiency, which can cause problems in red blood cells upon certain triggers, is the most common human enzyme defect, affecting over 400 million people, including over 1 in 10 Black Glucose 6 Phosphate Dehydrogenase, Redox Homeostasis and Embryogenesis Pathology of G6PD deficiency Pathology Made Simple Role of Glucose 6 Phosphate Dehydrogenase (G6PD) in the Pathophysiol ogy of Cataract.