TY - JOUR T1 - Type 3 antenatal Bartter syndrome presenting with mild polyuria JF - BMJ Case Reports JO - BMJ Case Reports DO - 10.1136/bcr-2021-242086 VL - 14 IS - 4 SP - e242086 AU - Yuto Otsubo AU - Yuji Kano AU - Hiroshi Suzumura AU - Shigemi Yoshihara Y1 - 2021/04/01 UR - http://casereports.bmj.com/content/14/4/e242086.abstract N2 - Bartter syndrome (BS) is a well-recognised inherited tubular dysfunction that causes polyuria, metabolic alkalosis and hypokalaemia. Among BS cases, antenatal/neonatal BS (ABS) usually shows distinct polyhydramnios prenatally and presents features of BS in the early neonatal period. We encountered a premature infant with type 3 ABS presenting with mild polyuria and discuss the pathogenesis of mild polyuria in type 3 ABS. A male infant was born at 31 weeks’ gestation. His mother received amniocentesis because of polyhydramnios. Hyponatraemia and hypokalaemia appeared within 3 days after birth. Metabolic alkalosis, hyperreninaemia and hyperaldosteronism were also identified. Temporary polyuria developed at 1 month after birth; however, the mean urine output during hospitalisation was within the normal range. CLCNKB compound heterozygous mutations were confirmed. Polyuria of type 3 ABS may be less severe than in other types of ABS. Lower urine sodium loss may be a characteristic feature of type 3 ABS. ER -