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

A novel DAX1 mutation (L381H) was discovered in the asymptomatic 8-month-old brother of a boy with primary adrenal failure. The infant had impaired adrenal reserve despite normal basal adrenal steroid concentrations. This case highlights the value of genetic testing in children at risk of the development of X-linked adrenal hypoplasia congenita before the onset of a potentially life-threatening adrenal crisis.