[Prenatal Bartter's syndrome. Report of two cases]

Antenatal Bartter Syndrome (ABS) is a rare autosomic recessive tubulopathy characterized by idiopathic hydramnios, fetal polyuria and elevated levels of amniotic chloride. It is related to mutations affecting several transporters in the loop of Henle e.g. the Na-K-2Cl cotransporter, the chloride channel CLC-NKB and the potassium channel ROMK. We report two cases of ABS in siblings born to consanguineous parents (first cousins). The first pregnancy showed hydramnios of unknown etiology at week 23. Two amnio drains were performed at weeks 26 and 27. The baby was born in week 29 and developed polyuria with hyponatremia, hypokalemia and hyperaldosteronism. After eliminating diabetes insipidus and adrenal insufficiency, ABS was diagnosed. The baby was treated with 0.5 mg/kg/d indomethacine, which controlled the polyuria and the hydroelectrolytic disorder. The second pregnancy showed idiopathic hydramnios at week 24. The elevated amniotic chloride level (above 112 mmole/l) led to the antenatal diagnosis of ABS. The mother was treated with 1 mg/kg/d indomethacine until week 31 in order to stabilize the hydramnios. Two amnio drains at weeks 31 and 33 allowed the pregnancy to be prolonged until week 34. A genetic study of the family showed homozygosity of the NKCC2 gene marker suggesting its implication in the disease.