Two genes, HNF4A (Hepatocyte Nuclear Factor 4 Alpha) and SLC2A2 (Solute Carrier Family 2 Member 2) causing renal Fanconi syndrome 4 and Fanconi-Bickel syndrome, respectively, are not yet classified due to the reduced number of cases published so far. The gene discussed is SLC2A2; the disease is glycogen storage disease due to GLUT2 deficiency.