Based on the level of residual enzyme activity, the World Health Organization (WHO) has categorized G6PD deficiencies into five classes: I (<10% of normal, chronic nonspherocytic hemolytic anemia); II (<10% of normal); III (10–60% of normal); IV (60–150% of normal), and V (>150% of normal) (WHO Working Group, 1989). This evidence concerns the gene G6PD and hyperinsulinemic hypoglycemia, familial, 4.