A significant increase in 2,3-BPG in red cells was described in a few patients with hemolytic anemia related to PGK deficiency (PGK Barcelona, PGK Matsue, PGK Amiens/New York and PGK Uppsala), because it has not been quantified in most of the described cases. This evidence concerns the gene PRKG1 and hyperinsulinemic hypoglycemia, familial, 4.