Presymptomatic diagnosis of X-linked adrenal hypoplasia congenita by analysis of DAX1

A novel DAX1 mutation (L381H) was discovered in the asymptomatic 8-month-ol d brother of a boy with primary adrenal failure. The infant had impaired ad renal reserve despite normal basal adrenal steroid concentrations; This cas e highlights the value of genetic testing in children at risk of the develo pment of X-linked adrenal hypoplasia congenita before the onset of a potent ially life-threatening adrenal crisis.