G6PD and hyperinsulinemic hypoglycemia, familial, 4: Glucose-6-phosphate dehydrogenase (G6PD) deficiency is an erythro-enzymopathy, recessive and one of the most common X-linked hereditary genetic defects, due to mutations in the G6PD gene, which cause functional variants with many biochemical and clinical phenotypes, affecting about 400 million people worldwide [1, 2].