The assumption that Gitelman syndrome is caused by an alteration in the thiazide-sensitive sodium-chloride co-transporter in the distal convoluted tubule has recently been proven by the identification of several mutations (mainly amino acid substitutions) in the SLC12A3 gene, where also a large number of deep intronic mutations could be linked with the development and/or progression of diabetic nephropathy [32, 35]. This evidence concerns the gene SLC12A3 and Gitelman syndrome.