Transient hyponatremia of prematurity caused by mild Bartter syndrome type II: a case report

Subhrata Verma,Guido Filler,Victoria Mok Siu,Rahul Chanchlani

doi:10.1186/s12887-020-02214-6

Abstract

BackgroundBartter syndrome subtypes are a group of rare renal tubular diseases characterized by impaired salt reabsorption in the tubule, specifically the thick ascending limb of Henle’s loop. Clinically, they are characterized by the association of hypokalemic metabolic alkalosis, hypercalciuria, nephrocalcinosis, increased levels of plasma renin and aldosterone, low blood pressure and vascular resistance to angiotensin II. Bartter syndrome type II is caused by mutations in the renal outer medullary potassium channel (ROMK) gene (KCNJ1), can present in the newborn period and typically requires lifelong therapy.Case presentationWe describe a case of a prematurely born female infant presenting with antenatal polyhydramnios, and postnatal dehydration and hyponatremia. After 7 weeks of sodium supplementation, the patient demonstrated complete resolution of her hyponatremia and developed only transient metabolic alkalosis at 2 months of age but continues to be polyuric and exhibits hypercalciuria, without development of nephrocalcinosis. She was found to have two pathogenic variants in the KCNJ1 gene: a frameshift deletion, p.Glu334Glyfs*35 and a missense variant, p. Pro110Leu. While many features of classic ROMK mutations have resolved, the child does have Bartter syndrome type II and needs prolonged pediatric nephrology follow-up.ConclusionTransient neonatal hyponatremia warrants a multi-system workup and genetic variants of KCNJ1 should be considered.

Highlights

Bartter syndrome subtypes are a group of rare renal tubular diseases characterized by impaired salt reabsorption in the tubule, the thick ascending limb of Henle’s loop
Bartter syndrome was initially described in 1962 by Bartter et al as a renal tubular disorder characterized by hypokalemia, metabolic alkalosis, a low or normal blood pressure and elevated renin [1]
A few cases of transient Bartter syndrome have been reported with mutations located in the melanoma-associated antigen D2 (MAGE-D2) gene located on the X-chromosome [2, 4, 5]

Summary

Introduction

Bartter syndrome subtypes are a group of rare renal tubular diseases characterized by impaired salt reabsorption in the tubule, the thick ascending limb of Henle’s loop. * Correspondence: guido.filler@lhsc.on.ca 1Department of Pediatrics, Schulich School of Medicine and Dentistry, University of Western Ontario, 1151 Richmond Street, London, ON N6A5C1, Canada 4Children’s Health Research Institute, 750 Baseline Road East, London, ON N6C 2R5, Canada Full list of author information is available at the end of the article can involve polyuria, polydipsia, normal to increased urinary calcium excretion, normal or mildly decreased serum magnesium, and occasionally hypophosphatemia. A few cases of transient Bartter syndrome have been reported with mutations located in the melanoma-associated antigen D2 (MAGE-D2) gene located on the X-chromosome [2, 4, 5].

Results

Conclusion