Further insights were derived from clinical data of patients with (1) GGM harboring different missense mutations in the SGLT1 gene [19, 201] (OMIM *182380), (2) GLUT2 deficiency (OMIM #227810), also known as Fanconi-Bickel syndrome (FBS), a rare disorder of glucose homeostasis that leads to accumulation of glycogen in the liver and kidney, glucose, and galactose intolerance [38, 104], and (3) familial renal glucosuria due to missense mutations in the SGLT2 gene (OMIM #233100) [109, 174]. The gene discussed is SLC5A2; the disease is glycogen storage disease due to GLUT2 deficiency.