Nephrocalcinosis in glucose-galactose malabsorption: nephrocalcinosis and proximal tubular dysfunction in a young infant with a novel mutation of SGLT1.

We report an association of proximal renal tubular dysfunction in a 50-day-old girl with glucose-galactose malabsorption who was found to have nephrocalcinosis, but no sign of nephrolithiasis. A novel homozygous nonsense mutation at 267Arg-->stop (CGA-->TGA) in the Na(+)-dependent glucose transporter (SGLT1) was found in loop 5 connecting transmembrane segments 6 and 7, indicating the complete loss of glucose transport activity. This case indicates that hypercalcaemia, nephrocalcinosis and proximal tubular dysfunction may be seen in association with glucose-galactose malabsorption and that most of these abnormalities improve with a glucose-galactose-free diet.