Cross-reactivity of adrenal steroids with aldosterone may prevent the accurate diagnosis of congenital adrenal hyperplasia.

During the first weeks of life, salt-wasting crisis, hyperkalemia, acidosis, hypoglycemia, and shock are the main findings of congenital adrenal hyperplasia (CAH). Pseudohypoaldosteronism type 1 (PHA1) is a rare disease of mineralocorticoid resistance, which is characterized with high aldosterone levels, hyponatremia and hyperkalemia without clinical findings of glucocorticoid deficiency. Patients with PHA1 are often initially diagnosed with CAH; however, it is unusual that a CAH patient is misdiagnosed as PHA1. In this report, we describe two cases with severe salt-losing crisis, hyperkalemia, and mild acidosis, which were initially diagnosed with PHA1, due to the high aldosterone levels along with normal adrenocorticotropic hormone and cortisol levels. However, subsequent investigation and genetic analysis led to the diagnosis of CAH with a homozygous I2 splice mutation in both alleles of the CYP21 gene. With this report, we emphasize that high blood levels of adrenal steroid precursors may cross-react with aldosterone and lead to confusing laboratory results that prevent making the accurate differential diagnosis between CAH and PHA1.