ESPE Abstracts

Introduction: Failure to thrive (FTT) is a common entity encountered by pediatricians. It can be caused by inadequate energy intake or “organic causes” such as inborn errors of metabolism or disorders of the endocrine system. One cause that is rarely seen is a deficiency of aldosterone.

Case presentation: A set of 3-month-old monozygotic male twins presented with failure to thrive and dehydration. Initially, they were evaluated for gastrointestinal/anatomical causes that were ruled out. They were also found to have persistent hyponatremia and hyperkalemia despite rehydration. Cortisol, corticotropin and 17-hydroxyprogesterone levels were normal. Aldosterone levels were undetectable in both twins, and plasma renin was normal. Gene sequencing of CYP11B2, the gene coding for the enzyme aldosterone synthase (AS), is currently pending. The patients were started on fludrocortisone 0.1 mg twice daily with sodium supplementation, which resulted in rapid improvement of electrolyte imbalances and growth.

Discussion: Hyponatremia and hyperkalemia in the setting of failure to thrive should elicit consideration of primary adrenal insufficiency, which in infancy is most commonly due to congenital adrenal hyperplasia (CAH). However, aldosterone deficiency and insensitivity may mimic the symptoms of CAH and should be considered as well. AS is only expressed in the zona glomerulosa of the adrenal cortex and is regulated by the renin-angiotensin system. The enzyme catalyzes the final three reactions of mineralocorticoid synthesis, which ultimately converts deoxycorticosterone to aldosterone.

Conclusion: We present a unique case of monozygous twins with aldosterone deficiency. While the differential of FTT in infants can be broad, the importance of identifying and treating rare causes of FTT can ultimately be lifesaving. We aim to highlight that although aldosterone deficiency is rare, it can mimic the electrolyte abnormalities of CAH. Genetic testing should also be pursued for the confirmation of biochemical diagnosis and genetic counseling.