# Autosomal Dominant Pseudohypoaldosteronism Type 1 in a Newborn With Failure to Thrive

## TL;DR

A newborn with poor growth and low sodium levels was diagnosed with a rare genetic disorder due to a new mutation in the NR3C2 gene.

## Contribution

The study reports a novel NR3C2 gene mutation causing autosomal dominant pseudohypoaldosteronism type 1 in a newborn.

## Key findings

- The infant showed clinical improvement with sodium supplementation.
- A new NR3C2 gene mutation (c.556_557del) was identified through genetic testing.
- The diagnosis was confirmed as autosomal dominant renal pseudohypoaldosteronism type 1.

## Abstract

Pseudohypoaldosteronism type 1 is a rare genetic disorder characterized by salt wasting and resistance to mineralocorticoids due to mutations in the NR3C2 gene which codes for the aldosterone receptor proteins in the kidneys. This case study involves an infant who presented with poor growth and significant hyponatremia. There was improvement in growth and correction of hyponatremia with sodium supplementation, later found to carry a new genetic variant causing autosomal dominant pseudohypoaldosteronism type 1. A 14-day-old newborn presented with failure to thrive, severe hyponatremia, mild hyperkalemia, and metabolic acidosis. The electrolyte abnormalities were corrected with intravenous fluid and sodium supplementation. Continued oral sodium supplementation led to improved weight gain. Clinical suspicion and subsequent diagnostic testing led to a diagnosis of the autosomal dominant renal form of pseudohypoaldosteronism type 1. Genetic testing revealed a novel mutation on the NR3C2 gene, c.556_557del (p.Met186Valfs*3). The baby was discharged home on supplemental sodium and high-calorie formula for catch-up growth. Outpatient follow-up is ongoing.