Severe Salt-Wasting in 16-day-old Male

Severe salt-wasting X-linked Adrenal Hypoplasia Congenita(X-AHC) is a rare cause of severe salt-wasting in affected males. We present a 16-day-old non-Hispanic male experiencing marked hyponatremia and hyperkalemia, initially thought to have 11-hydroxylase congenital adrenal hyperplasia(CAH). A 16-day-old male was born at term following an uncomplicated pregnancy, labor and delivery. Because of poor feeding, electrolytes were ordered revealing severe electrolyte imbalance. The child was assumed to have CAH due to elevation of cortisol precursors. He was treated with IV glucocorticoid and remained on IV fluids until his electrolyte balance and acidosis were corrected. These were replaced by oral glucocorticoid and mineralocorticoid, and salt supplementation was given orally. Once able to tolerate oral intake, IV fluids were tapered and subsequently discontinued. Based upon his family history, genetic testing was ordered, revealing a mutation in NROB1, consistent with a diagnosis of X-AHC. X-AHC may be misdiagnosed as CAH, but it is a rare disorder caused by a genetic mutation on the NR0B-1 (Nuclear Receptor B1) gene estimated to occur in 1:140,000 to 1:1,200,000 live births. Initial treatment of CAH and X-AHC are similar, requiring mineralocorticoid and glucocorticoid replacement. However, misdiagnosis may lead to life threatening electrolyte abnormalities following withdrawal of mineralocorticoid therapy in infants thought to have 11-OH-lase deficiency. Although less common than CAH, corrected identification of X-AHC allows proper management, appropriate genetic counseling, and anticipation of concomitant and future co-morbidities associated with X-AHC.