A 7-month-old developmentally normal girl presented with high fever and crying during micturition for 3 days. There was no history of convulsions, diarrhea, vomiting, lethargy or refusal to feed. She weighed 7.2 kg, blood pressure was normal, and she was hemodynamically stable. Anterior fontanelle was level, and there was no hepatosplenomegaly or dehydration. Urinalysis showed 100 neutrophils/HPF. Intravenous ceftriaxone was administered in view of a presumptive diagnosis of urinary tract infection; and continued for 14 days. Investigations revealed hemoglobin 11.2 g/dL, total leukocyte count 15×10⁹/L (70% neutrophils), and platelet count 2.1×10⁹/L. Blood urea was 12 mg/dL, and serum creatinine was 0.4 mg/dL. There was severe hyponatremia (serum sodium 110 mEq/L) while serum potassium was 5 mEq/L. Mild metabolic acidosis was observed on venous blood gas sample (pH 7.36, bicarbonate 16.2 mEq/L). Urine culture revealed significant growth of Escherichia coli. Since the genitalia were female, without any virilization, a diagnosis of type 1 pseudohypoaldosteronism (renal variety) secondary to the renal malformation and urinary tract infection, was considered. Serum aldosterone levels were 1696 pg/mL (reference range 20-1100 pg/mL), confirming pseudohypoaldosteronism. Sodium levels were restored to normal with 3% hypertonic saline supplementation.

Severe hyponatremia in infants may be part of salt losing crisis such as congenital adrenal hyperplasia, adrenal hypoplasia, or aldosterone resistance (pseudohypo-aldosteronism). Pseudohypoaldosteronism is characterized by renal tubular unresponsiveness to aldosterone and may complicate pediatric renal disorders such as obstructive uropathy, duplex kidneys, pyelonephritis, vesicoureteral reflux, tubulointerstitial nephritis etc [1-3]. The entity may manifest with hyponatremia, hyperkalemia and mild metabolic acidosis. Pyelonephritis and urinary tract malformations increase the intrarenal synthesis of cytokines such as Transforming Growth Factor b1 which can induce inhibition of action of aldosterone [4]. Impairment of the aldosterone receptor by circulating factors as well as bacterial toxins has also been proposed [5]. Hyperkalemia may not be noticed beyond the neonatal period in such cases [1]. Our patient had urinary malformation (duplex kidney) with pyelonephritis leading to transient Type 1 pseudohypoaldosteronism.

5. Kuhnle U, Guariso G, Sonega M, Hinkel GK, Hubl W, Armanini D. Transient pseudohypoaldosteronism in obstructive renal disease with transient reduction of lymphocytic aldosterone receptors. Results in two affected infants. Horm Res.1993;39:152-5.