Biochemical examination of mother's urine is useful for prenatal diagnosis of Bartter syndrome

Prenatal diagnosis of MAGED2 gene mutation causing transient antenatal Bartter syndrome

Transient antenatal Bartter syndrome due to melanoma-associated antigen D2 gene mutation is a newly reported type of Bartter syndrome. Its characteristics include an X-linked inheritance pattern, early-onset hydramnios, and spontaneous disappearance of symptoms after childbirth. To date, there have been no reports of prenatally diagnosed cases. We herein present the case of a preterm male born to a mother with early-onset hydramnios and a family history of X-linked idiopathic hydramnios. We suspected melanoma-associated antigen D2 gene mutation and performed direct sequencing. As a result, we were able to prenatally establish a diagnosis of transient Bartter syndrome due to a melanoma-associated antigen D2 gene mutation.

A Rare Cause of Refractory Severe Polyhydramnios: Antenatal Bartter Syndrome

Background: Antenatal Bartter syndrome is an autosomal recessive disorder causing severe polyuria that leads to severe polyhydramnios and preterm labor. Prenatal diagnosis of antenatal Bartter syndrome is difficult because the genetic diagnosis can only be confirmed following a clinical diagnosis in infants. Reports of prenatal diagnosis and treatment of antenatal Bartter syndrome are limited. Case Presentation: We present the case of a 33-year-old pregnant woman with refractory polyhydramnios at 31 weeks of gestation. There were no structural anomalies or placental problems on ultrasonography; therefore, antenatal Bartter syndrome was suspected. With repeated amniocentesis and indomethacin therapy, the pregnancy continued to 36 weeks of gestation. The clinical features of the infant and subsequent genetic testing confirmed the diagnosis of antenatal Bartter syndrome. The baby was in good clinical condition at the 3-month follow-up visit. Conclusions: For pregnant women with early onset and refractory severe polyhydramnios without morphological anomalies, antenatal Bartter syndrome should be highly suspected.

Antenatal bartter syndrome: a review

Antenatal Bartter syndrome (ABS) is a rare autosomal recessive renal tubular disorder. The defective chloride transport in the loop of Henle leads to fetal polyuria resulting in severe hydramnios and premature delivery. Early onset, unexplained maternal polyhydramnios often challenges the treating obstetrician. Increasing polyhydramnios without apparent fetal or placental abnormalities should lead to the suspicion of this entity. Biochemical analysis of amniotic fluid is suggested as elevated chloride level is usually diagnostic. Awareness, early recognition, maternal treatment with indomethacin, and amniocentesis allow the pregnancy to continue. Affected neonates are usually born premature, have postnatal polyuria, vomiting, failure to thrive, hypercalciuria, and subsequently nephrocalcinosis. Hypokalemia, metabolic alkalosis, secondary hyperaldosteronism and hyperreninaemia are other characteristic features. Volume depletion due to excessive salt and water loss on long term stimulates renin-angiotensin-aldosterone system resulting in juxtaglomerular hyperplasia. Clinical features and electrolyte abnormalities may also depend on the subtype of the syndrome. Prenatal diagnosis and timely indomethacin administration prevent electrolyte imbalance, restitute normal growth, and improve activity. In this paper, authors present classification, pathophysiology, clinical manifestations, laboratory findings, complications, and prognosis of ABS.

Bartter syndrome prenatal diagnosis based on amniotic fluid biochemical analysis

Bartter syndrome is an autosomic recessive disease characterized by severe polyuria and sodium renal loss. The responsible genes encode proteins involved in electrolyte tubular reabsorption. Prenatal manifestations, mainly recurrent polyhydramnios because of fetal polyuria, lead to premature delivery. After birth, polyuria leads to life-threatening dehydration. Prenatal genetic diagnosis needs an index case. The aim of this study was to analyze amniotic fluid biochemistry for the prediction of Bartter syndrome. We retrospectively studied 16 amniotic fluids of Bartter syndrome-affected fetuses diagnosed after birth, only six of them being genetically proven. We assayed total proteins, alpha-fetoprotein, and electrolytes and defined a Bartter index corresponding to the multiplication of total protein and of alpha-fetoprotein. Results were compared with two control groups matched for gestational age-non-Bartter polyhydramnios (n = 30) and nonpolyhydramnios (n = 60). In Bartter syndrome, we observed significant differences (p < 0.0001) for protein amniotic fluid levels when compared with the two control groups (1.55 g/L, 3.9 g/L, and 5.2 g/L, respectively) and low Bartter index (0.16, 0.82, and 1.0, respectively). No statistical difference was observed for electrolytes. In conclusion, Bartter syndrome can be prenatally suspected on amniotic fluid biochemistry (sensitivity 93% and specificity 100%), allowing appropriate management before and after birth.

Inherited Renal Tubulopathies Associated With Metabolic Alkalosis: Effects on Blood Pressure

Inherited tubular disorders associated with metabolic alkalosis are caused by several gene mutations encoding different tubular transporters responsible for NaCl renal handling. Body volume and renin-angiotensin-aldosterone system status are determined by NaCl reabsorption in the distal nephron. Two common hallmarks in affected individuals: hypokalemia and normal / high blood pressure, support the differential diagnosis. Bartter's syndrome, characterized by hypokalemia and normal blood pressure, is a heterogenic disease caused by the loss of function of SLC12A1 (type 1), KCNJ1 (type 2), CLCNKB (type 3), or BSND genes (type 4). As a result, patients present with renal salt wasting and hypercalciuria. Gitelman's syndrome is caused by the loss of funcion of the SLC12A3 gene and may resemble Bartter's syndrome, though is associated with the very low urinary calcium. Liddle's syndrome, also with similar phenotype but with hypertension, is produced by the gain of function of the SNCC1B or SNCC1G genes, and must be distinguished from other entities of inherited hypertension such as Apparently Mineralocorticoid Excess, of glucocorticoid remediable hypertension.

Elevated Aldosterone in Amniotic Fluid and Maternal Blood Has Diagnostic Potential in Pregnancies Complicated with a Fetus of Bartter Syndrome

Pregnancies with fetuses affected with the Bartter syndrome, an autosomal recessive disorder of hyperreninism and hyperaldosteronism, are complicated by early onset of polyhydramnios which results in preterm deliveries. We have assessed biochemical changes in amniotic fluid and the mother's blood with a view to early diagnosis. Aldosterone levels of both amniotic fluid and the mother's blood were found to be increased at 27 weeks of gestation, while electrolyte levels did not differ significantly from those reported earlier for controls. After birth the baby suffered from polyuria with hyponatremia, hypomagnesemia and hypercalciuria which could be controlled by treatment with sodium chloride and magnesium. Elevated aldosterone thus might be a useful marker for early diagnostic purposes.

Characteristic findings for diagnosis of baby complicated with both the VACTERL association and duodenal atresia

The VACTERL [vertebral defects (V), anal atresia (A), cardiac anomaly (C), tracheal-esophageal fistula with esophageal atresia (TE), renal defects (R), and radial limb dysplasia (L)] association can sometimes be diagnosed by ultrasonography and magnetic resonance imaging (MRI). Although the preaxial limb anomalies on ultrasonography were strongly associated with VACTERL association, the rate of limb anomalies is low. On ultrasonography, useful findings for prenatal diagnosis are a combination of esophageal atresia with hydramnion and renal anomalies. If esophageal atresia cannot be detected due to masking, diagnosis may be very difficult. In this case report, we reported the VACTERL association along with duodenal atresia. The detection of characteristic findings (enlarged stomach and duodenum, possibly change in gallbladder) by use of ultrasonography and MRI might be useful for the prenatal diagnosis of such cases.

Neonatal Bartter syndrome with unilateral multicystic dysplastic kidney disease

Neonatal Bartter syndrome is characterized by antenatal presentation with polyhydramnios. In this paper, we report a case of neonatal Bartter syndrome associated with unilateral multicystic dysplastic kidney disease. To our knowledge, this is the first case report of such an association.

Neonatal Bartter syndrome

A case of neonatal Bartter syndrome is reported. The baby born pre-term following a pregnancy complicated by polyhydramnios, presented at 7 months of age with failure to thrive, gastroenteritis and facial dysmorphisms. An unusual feature was the absence of the classical biochemical abnormality of hypochloremic alkalosis early in the course of the disease. Metabolic acidosis was the initial manifestation at 5 weeks of age. Awareness of this presentation is important to avoid delay in diagnosis and treatment.

Diagnosis and clinical biochemistry of inherited tubulopathies

Epithelial ion channels and transporter proteins have physiologically important roles throughout the length of the nephron. Discovering the molecular identities of tubular epithelial cell proteins and their functional roles has increased understanding of both renal physiology and tubular diseases. Defects in tubular handling of solutes may present with nephrocalcinosis or nephrolithiasis, rickets, acid base, electrolyte or blood pressure disturbances. Biochemical analysis of both serum and urine, together with clinical history and examination, remain fundamental for their diagnosis, whilst understanding of underlying molecular mechanisms allows appropriate management.