NR0B1 and X-linked adrenal hypoplasia congenita: X-linked adrenal hypoplasia congenita (AHC, OMIM 300200, ORPHA: 95702) is a potentially life-threatening disorder caused by defects in DAX1 (dosage-sensitive sex reversal-adrenal hypoplasia congenita critical region on X chromosome 1, gene 1), which is also known as NR0B1 (nuclear receptor subfamily 0, Group B, member 1; OMIM 300473), with a prevalence of one in 70,000 to 600,000 males [1–3].