Renal glycosuria is caused by an isolated inherited disorder of proximal tubule glucose reabsorption, which causes urinary glucose excretion at normal blood glucose levels. It is inherited as an autosomal recessive or dominant trait; most often as a mutation in the gene for sodium-glucose cotransporter 2 (SGLT-2). Secondary renal glycosuria usually develops as a consequence of toxic damage to the renal tubules, as one of the symptoms of Fanconi syndrome. In primary renal glycosuria there are no symptoms other than the glycosuria itself, which is most often detected incidentally. The daily loss of glucose may range from a several to ≥10 grams and is not accompanied by polyuria or polydipsia.
Diagnosis: Diabetes should be excluded; patients with renal glycosuria have normal glucose levels, both fasting and following a glucose challenge. All cases need confirmation that the glycosuria is not associated with another congenital or acquired proximal tubule defect, such as Fanconi syndrome.
Treatment is not necessary in primary renal glycosuria.
Prognosis is good; the defect has no clinical consequences.