The evidence for SGLT2 as a major pathway for renal glucose reabsorption has come from genetic studies of individuals with familial renal glucosuria (FRG), an autosomal recessive disorder of SLGT2. It has been almost a century since the first case has been described which causes glucosuria in the setting of a normal blood glucose concentration and the absence of other signs of renal tubular dysfunction. Different phenotypes have been described based on the extent of glucosuria. Individual and kindred studies have helped identify least 44 different mutations in the SLC5A2 gene. Long term follow up of these individuals has demonstrated no major health problems. However, given inconsistency of follow up and a small number of reported cases, it is difficult to infer the true extent of complications.