Bartter syndrome is a form of hyperaldosteronism that results from hypertrophy and hyperplasia of the juxtaglomerular cells, with normal blood pressure and hyperkalemic alkalosis without edema, increased renin concentration, angiotension II, and bradykinin. It is the manifestation of one of three genetic expressions: neonatal Bartter syndrome, classic Bartter syndrome, and Gitelman syndrome.

Bartter syndrome is extremely rare. The precise incidence is not known. The disease process is seen worldwide, with no exclusion of race and approximately equal occurrence in both sexes. The neonatal form is typically known before birth, whereas diagnosis of the classic form is typically made within the first 2 years of life.

Bartter syndrome predominately occurs as neonatal or classic forms. Neonatal Bartter syndrome (NBS) is subdivided into two types: type I NBS comes from a mutation in the sodium chloride/potassium chloride co-transporter gene; type II NBS comes from mutations in the ROMK gene. Classic Bartter syndrome develops as a result of mutation(s) in the chloride-channel gene (CIC-kb).

In each of these three subtypes a large volume of urine that is high in sodium, potassium, and chloride is delivered to the distal segments of the renal tubules. In that area only sodium is reabsorbed while potassium is secreted.

The characteristics of the disease are hypokalemia, hypochloremia, metabolic acidosis, and hyperreninemia (while the blood pressure remains normal). In both types of Bartter syndrome, classic and neonatal, the sentinel histologic finding is hyperplasia of the juxtaglomerular apparatus. Other histologic findings are listed in the box on the following page.