Barter Syndrome classification
Main article: Bartter syndrome

# Overview
Bartter Syndrome can be classified into five different types based on genotype. Bartter syndrome can result from homozygous or mixed heterozygous mutations in any of the genes. Thus, affecting the function of genes responsible for synthesis or membrane insertion of the transporters in the ascending limb of the loop of Henle. Mutation in NKCC2 gene results in impairment of sodium-potassium-chloride. cotransporter (Na-K-2Cl) in the apical membrane. Mutation in ROMK gene results in defective functioning of the luminal potassium channel. Mutation in the ClC-Kb gene results in the impairment of the basolateral chloride channel. Defects that reduce the activity of both ClC-Ka and ClC-Kb cause Bartter syndrome associated with sensorineural deafness (types IV and IVb). Type 5 Bartter syndrome results from a gain-of-function mutation in the Ca-sensing receptor (CaSR). A gain-of-function mutation in CaSR in the basolateral membrane of the thick ascending limb enhances the function of this receptor. This results in hypocalcemia and impairs sodium chloride transport. Bartter syndrome types 1, 2, and 4 present at a younger age. They present with symptoms, often quite severe in the neonatal period. Bartter syndrome type 3 also called classic Bartter syndrome present later in life and maybe sporadically asymptomatic or mildly symptomatic.

# Classification
- Bartter Syndrome can be classified into five different types based on genotype. Bartter syndrome can result from homozygous or mixed heterozygous mutations in any of the genes. Thus, affecting the function of genes responsible for synthesis or membrane insertion of the transporters in the ascending limb of the loop of Henle.
Bartter Syndrome type 1
- Bartter Syndrome type 1
- Mutation in NKCC2 gene results in impairment of sodium-potassium-chloride cotransporter (Na-K-2Cl) in the apical membrane.
- Bartter Syndrome type 2
- Mutation in ROMK gene results in defective functioning of the luminal potassium channel.
- Bartter Syndrome type 3
- Mutation in the ClC-Kb gene results in the impairment of the basolateral chloride channel.
- Type 3 is a severe salt-losing tubulopathy that develops when ClCKB becomes nonfunctional. ClCKB is a key determinant of tubular reabsorption of chloride and electrolytes along the distal tubule.
- Bartter Syndrome type 4
- Type IV results from the loss-of-function mutations in gene encoding barttin.
- Defects that reduce the activity of both ClC-Ka and ClC-Kb cause Bartter syndrome associated with sensorineural deafness (types IV and IVb).
- Bartter Syndrome type 5
- Type 5 Bartter syndrome results from a gain-of-function mutation in the Ca-sensing receptor (CaSR).
- A gain-of-function mutation in CaSR in the basolateral membrane of the thick ascending limb enhances the function of this receptor. This results in hypocalcemia and impairs sodium chloride transport.
- Initially, type V Bartter syndrome referred to autosomal dominant hypocalcemia (also called autosomal dominant hypoparathyroidism).
- Bartter syndrome types 1, 2, and 4 present at a younger age. They present with symptoms, often quite severe in the neonatal period.
- Bartter syndrome type 3 also called classic Bartter syndrome present later in life and maybe sporadically asymptomatic or mildly symptomatic.