A 1-year-old boy presented with polyuria, polydipsia and poor weight gain noticed since three months of age. He weighed 5 kg (-3SD), Height 64 cm (-3 SD), and had features of some dehydration. Hypernatremia (165 mEq/L) and metabolic acidosis (pH 7.27, bicarbonate levels 17 mEq/L) were detected. Serum creatinine, potassium, calcium, magnesium and chloride levels were within normal reference ranges. Serum osmolality and urine osmolality were 355 mOsm/L and 145 mOsm/L, respectively. He was diagnosed as nephrogenic diabetes insipidus after a vasopressin challenge test failed to increase the urine osmolality levels. Renal ultrasonography was normal. He was treated with spironolactone.

At the age of 3 years, he presented with rickets and hypocalcemic tetany (ionized calcium 2.2 mg/dL) in association with hypophosphatemia (2.2 mg/dL) and secondary hyperparathyroidism (PTH levels 180.2 pg/mL). The rickets was refractory to therapy with Vitamin D; and the child developed fractures of bilateral ulnae and femur requiring hip spica and plaster casts. He was still showing poor weight gain (weight 7.9 kg, -3SD). Triangular facies, prominent eyes and forehead, and large ears were appreciated. Blood pressure was normal. At this juncture, he was found to have hypokalemia (2.5 mEq/L), metabolic alkalosis (pH 7.52, bicarbonate levels 35.2 mEq/L) and hypercalciuria (spot calcium: creatinine ratio 1.4). Serum magnesium and creatinine levels were normal; urine chloride was >20 mEq/L. Plasma renin activity was high (38.9 ng/mL/h), confirming Bartter syndrome. Wrist X-ray showed metaphyseal cupping and splaying. Serum 25 hydroxycholecalciferol levels were 31.4 ng/mL. He is currently on potassium chloride (8 mEq/kg/day), indomethacin (2 mg/kg/day), enalapril (0.5 mEq/kg/day), and calcium supplements. At the last follow up at age of 4 years, his serum potassium, sodium, creatinine, calcium and phosphate levels are normal, and he is showing satisfactory weight gain.

The presentation of this child with Bartter syndrome is unusual for two reasons. The first being the initial paradoxical presentation with hypernatremic dehydration and metabolic acidosis; the second being the association with vitamin D resistant rickets (leading to secondary hyperparathyroidism). The former presentation has been anecdotally reported in the literature [1,2]. Bettinelli, et al. [1] reported a child who presented with severe hypernatremia, who was initially diagnosed as nephrogenic diabetes insipidus, but on follow up was diagnosed as Bartter syndrome. They concluded that in a few cases of Bartter syndrome, hypokalemia and/or metabolic alkalosis may be absent during the initial few years of life. Instead, atypical presentations such as hypernatremia and/or metabolic acidosis may be encountered. The latter atypical presentation in our case is the development of vitamin D resistant rickets in Bartter syndrome. This complication has been reported only twice in published literature long ago [3,4], and is a largely forgotten entity. It has been attributed to the calcipenic effect of hyperprostaglandinemia, or renal phosphate loss [3]. It is pertinent to note that in spite of deranged vitamin D metabolism, overt rickets is uncommon in Bartter syndrome [5].

Complications such as hypernatremia, metabolic acidosis and rickets can confound the clinical presentation of Bartter syndrome, and lead to a delayed diagnosis since pediatricians may not be familiar with such atypical presentations. The objective of this report is to create awareness regarding such atypical presentations, which highlight the phenotypic variability of Bartter syndrome.

Contributors: SK, AJ: were involved in management of the patients. Both authors contributed to drafting of the manuscript and approved the final version of the manuscript. SK: shall act as guarantor of the paper.

Funding: None; Competing interests:None stated.

1. Bettinelli A, Consonni D, Bianchetti MG, Colussi G, Casari G. Aldosterone influences serum magnesium in Gitelman syndrome. Nephron. 2000;86:236.

2. Chuang GT, Lin SH, Tsau YK, Tsai IJ. Antenatal Bartter syndrome resembling nephrogenic diabetes insipidus in a 5-year-old boy. J Formos Med Assoc. 2016;115:382-3.

3. Srivastava RN,　Singh G,　Agarwal R,　Moudgil A. Bartter’s syndrome with vitamin D-resistant rickets. Indian Pediatr.　1984;21:339-44.

4. Dillon MJ, Shah V, Mitchell MD. Bartter’s syndrome: 10 cases in childhood. Results of long-term indomethacin therapy. Q J Med. 1979;48:429-46.