A Case of Childhood-Onset Bartter Syndrome Type 1 with Renal Dysfunction

Bartter syndrome (BS, OMIM #601678) is a rare inherited salt-losing tubulopathy characterized by hypokalemia metabolic alkalosis with secondary renin-angiotensin-aldosterone system activation. As reported, BS type 1 is generally presented prenatal and neonatal period, and symptoms usually appear before and after birth or in infancy, accompanied by severe salt loss, whilst kidney function remains mostly normal. In this study, we report a case of BS type 1 with childhood onset and proteinuria and renal impairment. The child was born preterm due to hyperamniotic fluid, but there were no apparent symptoms after birth until the age of 3 when the child began to present with polydipsia, polyuria and increased nocturnal uria. At the age of 5, she had elevated serum creatinine level and proteinuria. After admission, she was diagnosed with chronic tubulointerstitial disease and stage 2 chronic kidney disease(CKD). According to the chloride clearance test, the abnormal function of medullary thick ascending limb Henle′s loop, was confirmed and BS type 1 was diagnosed by gene sequencing. After active management of complications, kidney function of the child improved. In the long-term follow-up, the urinary protein amount of the child still increased, eGFR slowly decreased, and the child was currently in the CKD2 stage. Children with prenatal BS may not present typical clinical manifestations immediately after birth until the onset of relevant clinical symptoms in childhood. BS type 1 patients may have renal impairment, which needs to be identified in time. Clinical differentiation diagnosis between BS and Gitelman syndrome can be made by chloride clearance tests. Early diagnosis and treatment are critical to improve prognosis.