An Infant With Hyponatremia, Hyperkalemia, and Faltering Growth: A Case Report.

Infants presenting with hyponatremia and hyperkalemia routinely engage clinician concern for congenital adrenal hyperplasia (CAH), a set of disorders resulting in difficulty producing glucocorticoids, mineralocorticoids, and sex steroids in the adrenal glands. However, we present the case of an infant with classic CAH-like symptoms, a negative newborn screen, and clinical features inconsistent with the diagnosis of CAH. Ultimately, the patient was diagnosed with pseudohypoaldosteronism (PHA), a condition in which aldosterone is unable to activate its receptor in the kidney. Notably, he also exhibited an uncommon complication of a left external iliac thrombus. Infants with hyponatremia and hyperkalemia without an immediately identifiable cause should be screened for urinary tract infection (UTI) and urinary tract malformations, and infants with severe urinary tract abnormality or malformation should have electrolytes monitored. This recommendation stems from the increased susceptibility of developing PHA in the setting of UTI without genitourinary tract malformation.