ESPE Abstracts

Introduction: Neonatal hyponatremia with hyperkalemia is an uncommon but potentially life-threatening occurrence. Congenital adrenal hyperplasia is often suspected in these cases, but among the alternative diagnoses, it is important to consider pseudohypoaldosteronism, a rare syndrome characterized by increased aldosterone secretion associated with clinical signs of hypoaldosteronism.

Case presentation: A 21-day-old female was admitted from an outside hospital for further evaluation of failure to thrive, hyponatremia and hyperkalemia. She was born at 37 weeks of gestation through IVF-ET from a gravida 2, para 1 woman, with no history of parental consanguinity. Her birth weight was 2.9 kg. For persistent weight loss (approximately 12%) and tendency to fall asleep, the newborn was transferred to the neonatal intensive care unit. Initial laboratory evaluation revealed serum sodium concentration 129 mEq/l, potassium 7,3 mEq/l, bicarbonate 26,2 mmol/l, creatinine 0,48 mg/dl. The electrocardiogram demonstrated normal cardiac activity. Results from laboratory studies obtained at presentation later showed renin 4786 microUI/ml (range 2-103,6 microUI/ml) and serum aldosterone markedly elevated at 2075 ng/dl (range 1,2-23,6 ng/dl). Serum cortisol, ACTH, 17-hydroxyprogesterone, and DHEA sulfate were normal. She had no evidence of virilization on physical examination. Renal ultrasound showed renal dimensions at the lower limits. Oral supplementation of sodium chloride was initiated at increasing dosage (from 2.3 meq/kg/day to 6 meq/kg/day). Due to the absence of acidosis in the blood gas analysis, in suspicion of a possible form of distal renal tubular acidosis, an attempt was made to wash out the sodium chloride supplementation. Subsequent blood gas analysis checks revealed progressive hyponatremia and parallel hyperkalemia. Therefore, sodium chloride supplementation was reintroduced, leading to subsequent normalization of serum electrolytes. The child subsequently responded well to sodium supplementation, and the dosage of 8.5 mEq/kg/day at the latest check normalized plasma renin, serum aldosterone concentration and serum electrolytes. In consideration of the clinical history and the trend of blood tests, the primary suspicion is pseudohypoaldosteronism; multidisciplinary endocrinological and nephrological follow-up will be essential to differentiate the secondary form of pseudohyperaldosteronism, potentially related to reduced renal size, from the primary form, for which genetic analysis will be necessary to confirm the diagnosis.

Conclusions: Although unusual, pseudohypoaldosteronism should be considered in the differential diagnosis for children with hyponatremic dehydration and hyperkalemia, even in the absence of acidosis in blood gas analysis. Managing these patients is challenging due to the lack of guidelines.