Introduction:
Renal glycosuria (MIM:233100) is a genetic disorder affecting glucose transport in the proximal renal tubules, characterized by isolated glycosuria despite normal blood glucose levels, a normal glucose tolerance test, and no other signs of proximal tubular dysfunction. The condition has a prevalence of 1 in 33,000 in the general population and affects both males and females equally. It results from pathogenic variants in the SLC5A2 gene (MIM:182381), which encodes a sodium/glucose cotransporter (SGLT2) responsible for reabsorbing glucose in the kidneys. As a result, glucose is excreted in the urine in significant amounts. Renal glycosuria can be inherited in autosomal recessive or autosomal dominant patterns, and recent studies suggest a codominant inheritance pattern with reduced penetrance may be the most accurate model.
The condition is often benign and asymptomatic, frequently identified incidentally. The presence of glucose in the urine creates an acidic environment conducive to bacterial growth, increasing the risk of infections, especially in the lower urinary tract. In this report, we describe the case of a six-year-old boy with recurrent urinary tract infections (UTIs) and failure to thrive, who was found to have renal glycosuria associated with a homozygous non-synonymous likely pathogenic variant in the SLC5A2 gene. This case represents the first documented instance of renal glycosuria in a child due to an SLC5A2 gene mutation in Sri Lanka.
Methods:
A six-year-old boy, the second child of healthy, non-consanguineous Sri Lankan parents with no family history of tubular dysfunction or other renal diseases, was found to have isolated asymptomatic glycosuria during an evaluation for recurrent UTIs and failure to thrive. The child was developmentally normal and not on any long-term medications. He exhibited no symptoms or signs indicative of diabetes or underlying renal disease. On clinical examination, his weight was 16.5 kg (<5th percentile), height 108 cm (<-2 SD), and BMI 13.09 kg/m² (<-2 SD), with normal blood pressure and other vital signs. Serial urine tests revealed the presence of sugar (1.5 g/dl) but no albumin. His fasting blood glucose was 70 mg/dl, and random blood glucose was 80 mg/dl. Renal function tests and an ultrasound of the kidneys were normal.
Results:
Genetic testing was performed on the proband following pretest counselling and with parental written informed consent. Genomic DNA was extracted from peripheral venous blood, and whole exome sequencing was conducted. Analysis of the SLC5A2 genomic sequence identified a homozygous non-synonymous likely pathogenic variant, denoted as NM_003041.4.950G>A at the cDNA level, located in exon 8 of the SLC5A2 gene. The variant detected in our patient in exon 8 of the SLC5A2 gene results in the substitution of cysteine by tyrosine at position 317 of the amino acid sequence. The fact that this residue was found to be highly conserved among the human SGLT family members and across SGLTs of various other species suggests that this position may be of particular functional importance.
It was concluded that the child's failure to thrive was due to recurrent UTIs associated negative energy intake. As a preventive measure, the child was started on prophylactic antibiotics to prevent further UTIs.
Conclusions:
Renal glycosuria is generally a benign condition but is a diagnosis of exclusion that must be considered after ruling out other causes of glycosuria. Genetic testing can confirm the diagnosis, aid in counselling, and assist in predicting outcomes.
I have no potential conflict of interest to disclose.
I did not use generative AI and AI-assisted technologies in the writing process.