ESPE Abstracts

Introduction: Bartter syndrome type 2, is a rare genetically heterogenous disorder characterized by mutations in the KCNJ1 encoding the ROMK channel. This channel ensures adequate luminal potassium availability for the efficient functioning of the Na-K-2Cl co-transporter which is involved in salt reabsorption. Homozygous mutation in KCNJ1 commonly present with transient pseudohypoaldosteronism in the early neonatal period due to loss of ROMK function. We present a unique case of antenatal Bartter syndrome presenting with transient pseudohypoaldosteronism, failure to thrive and hypocalcaemic hypercalciuria, highlighting the challenges in diagnosis and management.

Case Presentation: A 15-day-old girl, born at 34 weeks gestation to non-consanguineous parents with a weight of 1.4 kg, was found to have hyponatraemia and hyperkalaemia, prompting referral to an endocrinologist. A family history of unexplained neonatal death associated with polyhydramnios and prematurity was noted. After excluding congenital adrenal hyperplasia, the patient was initially treated for transient pseudohypoaldosteronism with fludrocortisone. USS KUB revealed echogenic kidneys and unilateral pelvicalyceal dilatation, leading to nephrology consultation. Over the first year, she developed hypokalemia but blood gas analysis was normal. Subsequently developed bilateral nephrocalcinosis with hypercalciuria. Over time developed polyuria, hypokalaemic metabolic alkalosis with hypocalcaemic hypercalciuria. Whole exome sequence revealed biallelic KCNJ1 c.914G>A(p.Ser305Asn), variant of uncertain significant REVEL score approximating 1 indicating possible pathogenic outcome. She was started on indomethacin. Potassium and calcium doses were adjusted according to the response. Interestingly her parathyroid hormone level which was high initially started normalizing with appropriate treatment.

Conclusion: Bartter syndrome type 2 presents a diagnostic challenge, particularly when initial symptoms mimic other conditions. Notably, hypercalciuria is characteristic of this syndrome, suggesting that the hypocalcaemia observed may have resulted from polyuria-associated hypercalciuria. Genetic testing plays a pivotal role in unraveling such complexities, guiding targeted therapeutic interventions to alleviate symptoms and improve patient outcomes. Early recognition and tailored management are paramount in mitigating the morbidity associated with rare genetic disorders.