CLCNKB and Bartter disease type 3: The classic Bartter syndrome (Bartter syndrome type III) is caused by a mutation in the gene CLCNKB encoding the chloride ion channel ClC-Kb located in the thick segment of the ascending branch of the medullary loop.[13] Patients with Bartter’s syndrome are more likely to experience growth and development delay before the age of 3, with normal blood magnesium levels and normal or high urinary calcium levels.