Antenatal Bartter syndrome type 1

Antenatal Bartter syndrome is characterized by polyuria that starts before birth, which signifies by polyhydramnios. The molecular genetic background are autosomal recessive inactivating mutations of the SLC12A1 gene.

Epidemiology

Although exact figures still unknown and difficult to obtain, the the incidence is thought between 1 in 50,000 to 1 in 100,000.

Clinical Findings

The clinical diagnosis is suspected when polyhydramnios is observed since about the 25th week of gestation. It may require amniocentesis. Renine and aldosterone levels are elevated in the amniotic fluid. Often polyhydramnios causes preterm delivery. Beginning with the first day of life excessive water and salt losses originates additional systemic clinical problems such as fever, vmoting, and diarrhoea.

Besides the typical Bartter symptoms (hypokalemia, metabolic alkalosis, hyperreninemic hyperaldosteronism, normal blood pressure, and hyperkaliuria), antenatal Bartter syndrome is characterized by hypercalciuria that brings about nephrocalcinosis often seen in utero already.

Indometacine therapy is highly effective and sometimes prevents spironolactone or potassium supplementation.

Growth retardation is common and there are patients in which it becomes impossible to maintain normal biochemical parameters.

Diagnosis

The diagnosis requires a thorough study of all solutes in plasma and urine as it is required for all Bartter syndromes. Additionally urine levels of prostaglandines PGE2 und PGF2alpha are helpful.

Molecular genetic testing allows to differentiate the exact type of Bartter syndrome which has implications for disease management.

Systematic

Bartter syndrome
	Antenatal Bartter syndrome type 1
		SLC12A1
	Antenatal Bartter syndrome type 2
	Classic Bartter syndrome
	Hypercalciuric hypocalcemia 1
	Hypercalciuric hypocalcemia 2
	Infantile Bartter syndrome with deafness type 4
	Transient antenatal Bartter syndrome