A novel MAGED2 variant in a Chinese preterm newborn with transient antenatal Bartter’s syndrome with 4 years follow-up

Background Transient antenatal Bartter’s syndrome caused by MAGED2 mutation is a rare X-linked recessive renal tubular disorder. Cases reported are mostly infants, and the long-term prognosis of the disease is still under investigation. Case presentation We encountered a preterm male infant with polyhydramnios, polyuria, salt loss, hypercalciuria, nephrocalcinosis and alkalosis. Antenatal Bartter’s syndrome was suspected, but these clinical symptoms surprisingly disappeared after about 2 months. This led to the clinical diagnosis of transient antenatal Bartter’s syndrome. Gene analysis in this patient disclosed a novel variant (c.1598C > T, p.Ala533Val) in exon 12 of MAGED2 gene, and his mother was a heterozygous carrier. This patient was followed up in clinic for 4 years without recurrence of imbalance of potassium, sodium and chloride. His height and weight were in normal range, and all laboratory examinations and nephrotic ultrasound were also normal. Conclusions We reported the first Chinese case of transient antenatal Bartter’s syndrome caused by MAGED2 mutation. The 4-year follow-up of our case further demonstrates the benign prognosis of the disease and indicates that early recognition of this phenotype could avoid unnecessary treatments.

A Case Report and Literature Review of a Novel Mutation in the MAGED2 Gene of a Patient With Severe Transient Polyhydramnios

Background: Polyhydramnios occurs frequently during pregnancy. Mutations in the MAGED2 gene can cause X-linked acute early-onset polyhydramnios with a severe but transient form of antenatal Bartter's syndrome.Case Presentation: Here, we report a new novel frameshift mutation c.733_734delCT (p. Leu245GlufsTer4) in the MAGED2 gene (NM_177433.1) that caused prenatal polyhydramnios, but did not cause polyuria after birth. Follow-up was conducted for 2 months, and the baby's growth and development were normal, without polyuria and renal impairment. In addition, we identified all individuals with MAGED2 mutations reported in the literature before March 2021.Conclusion: We report a new case with a novel variant of the MAGED2 gene that caused severe hydramnios but with a good result and summary clinical characteristics in a newborn with antenatal Bartter's syndrome caused by an MAGED2 mutation. Good prenatal diagnosis and genetic consultation can improve pregnancy monitoring and newborn management.

A common NKCC2 mutation in Costa Rican Bartter's syndrome patients: evidence for a founder effect.

Bartter's syndrome involves an overlapping set of closely related renal tubular disorders that can be subdivided into at least three clinical phenotypes: (1) the hypercalciuric antenatal Bartter variant; (2) the classic Bartter variant; and (3) the hypocalciuric-hypomagnesemic Gitelman variant. Recent data demonstrate that in several phenotypically indistinguishable cohorts, antenatal Bartter's syndrome is genetically heterogeneous. In these patients, mutations in the genes encoding either the bumetanide-sensitive Na-K-2Cl cotransporter (NKCC2) or the ATP-regulated potassium channel ROMK (KCNJI) have been identified. A cohort of 20 Costa Rican patients with a congenital syndrome that bears strong similarities to antenatal Bartter's syndrome but also has several distinct features has recently been described. In this cohort, we have identified a predominant mutation that introduces a premature stop in codon W625 of the NKCC2 gene (SCL12A1). This mutant allele is contained on a single common haplotype, suggesting that the majority of antenatal Bartter's syndrome patients in Costa Rica share a single common ancestor.