What is renal glucosuria?

Updated: Dec 10, 2018
  • Author: Rajendra Bhimma, MBChB, MD, PhD, DCH (SA), FCP(Paeds)(SA), MMed(Natal); Chief Editor: Craig B Langman, MD  more...
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Answer

Renal glucosuria is the excretion of glucose in the urine in detectable amounts at normal blood glucose concentrations in the absence of any signs of generalized proximal renal tubular dysfunction due to a reduction in the renal tubular reabsorption of glucose. The revised criteria for diagnosis of this condition includes: a normal oral glucose tolerance test in regard to plasma glucose concentration, normal plasma levels of insulin, free fatty acids, glycosylated hemoglobin, and relatively stable urinary glucose levels (10 to 100 g/d; except during pregnancy, when it may increase) with glucose present in all urine samples. The urine should contain glucose as the only source of carbohydrate, and individuals should have normal carbohydrate storage and use.

The inherited form of this disorder is called familial renal glucosuria (FRG) (PRG; OMIM #233100). FRG is a rare disorder due mainly to mutations in the sodium-glucose cotransporter 2 gene (SGLT2) that are responsible for the majority of cases. [1, 2, 3, 4]

To date over seventy mutations have been identified including missense mutations, nonsense mutations, small deletions and splicing mutations.  Most however are missense mutations. It is usually inherited in a co-dominant fashion with incomplete penetrance. Although the pattern of inheritance that best fits FRG is one of co-dominance, increased glucose excretion was not observed in all individuals with similar or identical mutations.  Heterozygosity for mutations suggest a role of nongenetic factors or other genes involved in renal glucose transport. [5]

The SGLT2 gene is localized to p11.2 on chromosome 16.  It consists of 14 separate exons spanning approximately 7.7kb of genomic DNA, and encodes the 672 amino acid protein SGLT2.  Glucosuria in these patients can range from < 1 to >150g/1.73m2 per day (normal value: range 0.03 to 0.3g/d). 

 

In general, renal glucosuria is a benign condition and does not require any specific therapy. Glucosuria may also be associated with tubular disorders such as Fanconi-de Toni-Debre syndrome, cystinosis, Wilson disease, hereditary tyrosinemia, or oculocerebrorenal osteodystrophy (Lowe syndrome). Renal glucosuria has also been reported in patients with acute pyelonephritis in the presence of a normal blood glucose level. Glucose loss in the urine may vary from a few grams to more than 100g (556 mmol) per day.


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