The facilitative glucose transporters have isoforms GLUT 1 to 5. GLUT2 is mainly associated with glucose transport in the convoluted portion of the proximal tubule. Glucose reabsorption is age dependent. In premature infants of fewer than 30 weeks gestation, glycosuria is quite common, because the filtered load of glucose delivered to the kidney often is too high for the immature nephron to handle. This variability arises from variation in the length of the proximal tubule and differences in glomerular size and location.
Medical history offers no clues for either primary or benign renal glycosuria.
Renal glycosuria is first noted on routine urinalysis. In cases of glycosuria associated with tubular disorders, a history of growth failure, polyuria, polydipsia, or dehydration may exist. The inheritance pattern is autosomal recessive, although autosomal dominance has been reported. Type A is so-called classic glycosuria, with reduction in both glucose threshold and maximal glucose reabsorption rate. In Type B, there is a reduction in the glucose threshold, normal reabsorptive rate, and an increased splay.