Identification of a novel form of renal glucosuria withoverexcretion of arginine, carnosine, and taurine

Abstract

Glucosuria occurs in diabetes mellitus, generalized proximal tubular dysfunction of Fanconi's syndrome, glucose-galactose malabsorption syndrome, and primary renal glucosuria. Patients with primary renal glucosuria have normal blood glucose levels, normal oral glucose tolerance test results, and persistent glucosuria that may approach the filtered load of glucose in the most severe cases. The primary defect is proposed to be in the sodium-glucose cotransporter type-2 (SGLT2) located in the apical membrane of S1 segment proximal renal tubule cells. Primary renal glucosuria is classified as types A, B, or O based on the characteristics of the transport defect. The magnitude of glucosuria has varied from 20 to 150 g of glucose excreted in 24 hours. Described inheritance patterns have included both autosomal dominant and autosomal recessive mechanisms. Some cases have been associated with selective aminoaciduria, distinctly unlike the generalized aminoaciduria seen in Fanconi's syndrome. We report the first case of primary renal glucosuria with selective overexcretion of arginine, carnosine, and taurine. This case may represent a genetic defect unique from the abnormalities in previously described cases of primary renal glucosuria with different amino acid excretion patterns. Future investigations could determine whether the syndrome involves a defect in the SGLT2 gene.