Endocrine Abstracts

Introduction: Bartter syndrome (BS) is a rare autosomal recessive disorder, with an estimated prevalence of 1 in 1.000.000. It is characterized by a primary defect in sodium chloride reabsorption in the medullary thick ascending limb of Henle’s loop. Severe hypokalemia, metabolic alkalosis, hyponatremia, hypochloremia, hyperaldosteronism, and increased urinary loss of sodium, potassium, and chloride can raise the suspicion of BS, but genetic testing is required for a definitive diagnosis. Correct diagnosis and early treatment prevent the impairment of renal function, the development of complications and improve the prognosis.

Case report: We present the case of a 3 years and 7 months-old boy, admitted to our Pediatric Endocrinology Department for short stature (H=87 cm, -3.32 SD), underweight (W=9.5 kg) and massive polyuria-polydipsia syndrome (ingestion volume=5000-7000 ml/day and urine volume=4000-5000 ml/day) with normal blood pressure. He is the first child of non-consanguineous parents, born prematurely by cesarian section at 32 weeks gestation, appropriate for gestational age, with perinatal asphyxia requiring intensive care. Severe unexplained polyhydramnios was diagnosed in the second trimester and required 3 amnioreductions. During his first 3 years of life, he had multiple hospitalizations in the Pediatric Gastroenterology department where celiac disease, mucoviscidosis and intestinal parasitosis were excluded. In our department, the laboratory tests revealed metabolic alkalosis, hypokalemia, hyponatremia, a high urinary calcium/creatinine ratio and a high urinary potassium/creatinine ratio. Hormonal evaluation identified normal for age thyroid, adrenal and gonadal function, with a possible growth hormone (GH) deficiency (low baseline GH and IGF-1), as well as an elevated copeptin value. The abdominal ultrasound showed bilateral medullary nephrocalcinosis and the brain MRI was normal. As the clinical diagnosis of BS was established, he was started on potassium chloride supplementation and was referred to the Pediatric Nephrology Department where indomethacin was added. The genetic testing detected 3 pathogenic variants in the SLC12A1 gene, confirming BS type I. At the six months follow-up, we noted a reduction of polyuria (=3500 ml/day) and polydipsia (=4000 ml/day), with improved weight gain, while plasma potassium and bicarbonate levels normalized.

Conclusions: Despite being rare in clinical practice, the diagnosis of BS should be considered in any premature neonate with unexplained polyhydramnios and in any child with growth failure, hypokalemia, polydipsia and polyuria. Correct diagnosis and early treatment improve the quality of life of these children, allowing them to reach their full growth potential. Genetic testing helps to establish a specific diagnosis and provides the basis of genetic counseling for family members.