Identification of Three Novel MAGED2 Variants Causing Antenatal Bartter Syndrome in Three Chinese Families

Background/Objectives: We aimed to report three novel MAGED2 variants associated with transient antenatal Bartter syndrome (TABS) and to summarize the prenatal and postnatal features of MAGED2-related TABS through case analysis and literature review. Methods: Three unrelated Chinese families with polyhydramnios-affected pregnancies underwent genetic testing. Clinical data, including prenatal imaging, delivery details, and postnatal outcomes were reviewed. A literature review of reported MAGED2 variants and associated phenotypes was conducted. Results: Three previously unreported MAGED2 variants were identified: two frameshift variants (c.1511del p.Gly504Alafs*72 and c.338del p.Pro113ArgfsTer4) and one deletion (chrX:54,820,664–54,839,053 GRCh37). All fetuses presented with polyhydramnios; two were large for gestational age (LGA). Additional findings included ventriculomegaly and scrotal enlargement. Two male infants were delivered at 33 weeks following repeated amnioreduction, with transient postnatal electrolyte abnormalities and normal neurodevelopment at 3 and 4 years. One fetus with a frameshift variant died in utero at 26 + 1 weeks. A literature review of 53 cases revealed 38 distinct MAGED2 variants, predominantly null variants (65.8%). Polyhydramnios was the most consistent antenatal sign. No intellectual disability was reported in surviving individuals. Conclusions: These findings expand the MAGED2 mutational spectrum. Polyhydramnios and LGA represents the most frequent features in TABS. In fetuses presenting with early-onset severe polyhydramnios (around 19–20 weeks of gestation), particular attention should be paid to possible exon-level or partial deletions involving MAGED2 during genetic evaluation.