Hypocalcemia as the Initial Presentation of Type 2 Bartter Syndrome: A Family Report
2Armon Child Health Center, Clalit Health Services
3Division of Endocrinology and Diabetes, Center for Bone Health, The Children’s Hospital of Philadelphia
4Center for Applied Genomics, The Children’s Hospital of Philadelphia
5Pediatric Ward B, Ha’Emek Medical Center
6The Rappaport Faculty of Medicine, Technion Institute of Technology
7Pediatric Nephrology Unit, Ha’Emek Medical Center
Bartter syndrome (BS) is a group of rare autosomal-recessive tubulopathies characterized by hypokalemic, hypochloremic metabolic alkalosis in which the primary defect is a deficiency of transporters involved in sodium chloride reabsorption. Type 2 BS results from a defect in the renal outer medullary potassium channel encoded by the KCNJ1 gene. Type 2 BS presents with polyhydramnios, intrauterine growth retardation, prematurity, failure to thrive, polyuria, hypercalciuria, and life-threatening episodes of dehydration. Hypocalcemia is a very rare presenting symptom of BS, with only a few published cases reporting it as the initial manifestation of type 2 BS.
Aim:
To describe a child who presented with hypocalcemic seizure at the age of 2.3 years that was first related to vitamin D deficiency and high-phosphate soft drink consumption.
Methods:
Whole exome sequencing (WES) was used to evaluate the biochemical abnormalities of the proband.
Results:
We identified a previously described homozygous missense mutation c.212C>T, p.T71M in the KCNJ1 gene associated with type 2 BS. Six additional family members with the same mutation and diagnosed clinically with BS are also reported, two presenting with hypocalcemia associated with vitamin D deficiency
Conclusion:
This report expands the clinical spectrum associated with KCNJ1 mutations and emphasizes the role of WES in unsolved cases of hypocalcemia when genetic disease is suspected. It also highlights the hazardous effects of phosphate-containing soft drinks on calcium metabolism.
