Adrenal Hypoplasia Seemingly First as a Primary Hypoaldosteronism

Background: X-linked Congenital Adrenal Hypoplasia (AHC) is a rare cause of primary adrenal insufficiency due to mutations in NR0B1 gene, causing a loss of function of the nuclear receptor protein DAX-1. Adrenal insufficiency usually presents in the first two months of life, but sometimes can appear later in childhood. Hypogonadotropic Hypogonadism is often associated later in life and all patients develop azoospermia. We describe an unusual onset of AHC started with isolated hypoaldosteronism as first and only sign of disease. Case presentation: A 18-days-old newborn presented with failure to thrive and feeding difficulties. Blood tests showed severe hyponatremia, hyperkalemia and hypochloremia. Renin was found over the measurable range and aldosterone was low whereas cortisol level was normal with a slightly increased ACTH. In the suspicion of Primary Hypoaldosteronism, correction of plasmatic electrolytes and replacement therapy with Fludrocortisone were promptly started. The subsequent evidence of low plasmatic and urinary cortisol and increased ACTH required the start of Hydrocortisone replacement therapy and it defined a clinical picture of adrenal insufficiency. Genetic analysis demonstrated a novel mutation in DAX-1 gene leading to the diagnosis of AHC. Conclusions: NR0B1/DAX-1 mutations should be considered in male infants presenting with isolated hypoaldosteronism as first sign of adrenal insufficiency.