Isolated primary glucosuria without SGLT2 mutation: A case report

Primary renal glucosuria typically results from SLC5A2 mutations affecting SGLT2 and manifests as isolated urinary glucose excretion with normoglycemia. Rarely, sustained glucosuria occurs in the absence of known genetic mutations or systemic disease.

A 63-year-old male with well-controlled stage 3 chronic kidney disease displayed lifelong glucosuria (urine glucose +50 to +100 mg/dL), beginning at age 18, with persistently normal HbA1c and no history of diabetes or systemic symptoms. Investigations showed isolated glucosuria on repeated urinalyses, minimal nonspecific amino acid changes, and negative targeted genetic testing for SLC5A2. He was diagnosed presumptively as primary renal glucosuria of unknown genetic etiology. The patient remains asymptomatic under conservative follow-up.

This uncommon presentation of long-standing isolated glucosuria without SLC5A2 mutations highlights the need for broader genetic assessment, potentially whole-exome sequencing and enriched understanding of alternative renal glucose transport mechanisms.