Our understanding of Gitelman syndrome (GS) and Bartter syndrome has continued to evolve with the use of genetic testing to more precisely define the tubular defects responsible. GS is caused by mutations in the SLC12A3 gene encoding the Na+–Cl− co-transporter of the distal convoluted tubule (NCCT) and tends to be associated with a milder salt-losing phenotype. We describe two female siblings presenting in infancy with a severe salt-losing tubulopathy and failure to thrive due to compound heterozygous mutations in the SLC12A3 gene encoding the NCCT. Both children were treated with indomethacin resulting in improved linear growth and polyuria. Some atypical biochemical findings in our cases are discussed including raised urinary prostaglandin (PGE2) excretion that normalized with intravenous fluid repletion.