Patient with adrenal insufficiency due to de novo mutation in the NR0B1 gene

Objectives: X-linked congenital adrenal hypoplasia is a rare disease with a known genetic basis, presenting with adrenal insufficiency and hypogonadotrophic hypogonadism and variable clinical expression. Case report: 26-day-old male patient was admitted with symptoms compatible with adrenal insufficiency, hyponatremia and hyperkalemia, requiring serum therapy with NaCl supplementation and fludrocortisone, achieving clinical stability. Congenital adrenal hyperplasia was ruled out after measurement of 17-OH-progesterone. The rest of the hormones were within the reference ranges, except for adrenocorticotropic hormone (ACTH), which was significantly higher, and aldosterone, which was lower. In the following analyses, very long chain fatty acids were studied to rule out adrenoleukodystrophy, the CYP11B2 gene (aldosterone synthase), and an MRI was performed to rule out other morphological alterations. All these tests were normal. Finally, after detecting cortisol deficiency in a blood test, a more extensive genetic study was performed which described a mutation in the NR0B1 gene, establishing the diagnosis of congenital adrenal hypoplasia. Conclusions: Congenital adrenal hypoplasia is a disease with a complex diagnosis due to the variability in clinical expression and the degree of alteration of laboratory tests, requiring exhaustive follow-up and genetic testing to reach the diagnosis.