Coexistence of hypomagnesaemia and hypocalciuria in GS, and less frequently in BS type 3, suggests that the dissociation of renal calcium and magnesium handling may not always be caused by NCCT dysfunction as originally thought, but possibly because of a more general impaired transcellular salt reabsorption in the DCT involving CLC-Kb [3]. This evidence concerns the gene SLC12A3 and Bloom syndrome.