Abstract
Introduction: The presence of glucosuria is usually a red flag that leads to diabetes mellitus screening in pediatric patients. Despite this correct approach, high levels of glucosuria without hyperglycemia should raise suspicion for other diagnoses, namely renal tubular disease, such as Familial Renal Glucosuria (FRG).
A large number of mutations on the solute carrier family 5 member 2 (SLC5A2) gene, which encodes sodium-glucose cotransporter 2 (SGLT2), have been reported to be responsible for the increase in renal excretion of glucose.(1)
Case Report: We report a case of a teenager, followed in our outpatient clinic for Hypokalemic Periodic Paralysis type 2 (HyPP2), in which persistent renal glucosuria was fortuitously found. Genetic testing for SLC5A2 gene was conducted, leading to the identification of two mutations in the SGLT2 gene, both in heterozygosity, one in exon 14 (N654S), previously reported, and another in exon 2 (A94C), a novel mutation not yet described in population databases.
Discussion: The fact that our patient had mutations in two different genes from different chromosomes, both related to sodium channels and one of these not previously described, makes this case interesting. The key point is that it is important to be aware of these diseases and assess the child as a whole. Despite the apparent benignity of these two diseases, clinical surveillance must be tight. We advise avoiding prolonged fasting, a diet rich in carbohydrates and intense physical exercise.
Conclusion: In the presence of isolated glucosuria, without hyperglycemia, we should suspect Familial Renal Glucosuria. Familial Renal Glucosuria is a rare disease caused by mutation in SGLT2 gene. Exon 2 (A94C) in heterozygosity is a novel mutation not yet described in population databases. This is the first description of a patient with both Familial Renal Glucosuria and Hipokalemic periodic paralysis type 2. The association of both these diseases had not yet been reported.

Key words: Hypokalemic Periodic Paralysis type 2, renal glucosuria, Familial Renal Glucosuria, novel mutation.