What causes an infant to have bartters syndrome?

Bartter syndrome, which results in low potassium levels,
deceased blood acidity, and normal to low blood pressure, is a rare defect in the thick
ascending limb of the loop of Henle.  It is an inherited
syndrome.

In most cases (neonatal) t shows up between weeks
24 and 30 of gestation.  It is detected by an excess of amniotic fluid.  In the other
small percent of cases (classic)  it doesn't really start to be noticed until 5 or 6
years of age.

The cause of the syndrome is mutations of
genes that encode the proteins that transport ions across renal cells i the thick
ascending limb of the nephron.  There are several genes that could possible mutate,
causing a different type of Bartter syndrome:

Type 1 -
defect in the NA-K-2Cl symporter of the NKCC2 gene
Type 2 - defect in the
thick ascending limb K+ channel of the ROMK gene
Type 3 - defect in the Cl-
channel of the CLCNKB gene
Type 4 - defect in the Cl- channel of the BSND
gene
Type 5 - defect in the calcium- sensing receptor in the CASR
gene