Infantile Growth Hormone Deficiency and X- Linked Adrenal Hypoplasia Congenita

X-linked adrenal hypoplasia congenita (AHC) is a rare but important cause of primary adrenal insufficiency and can be associated with significant morbidity and mortality. AHC is caused by mutations within the NROB1 gene that codes for the DAX-1 protein, an orphan nuclear receptor essential for the development of the hypothalamic-pituitary-adrenal axis. Affected individuals typically present in early infancy with adrenal insufficiency and growth is usually normal once medical therapy is instituted. Here we report the first case of growth hormone deficiency in an infant with AHC and a novel NROB1 missense mutation.

A two-week old infant presented with salt-losing adrenal crises and a normal newborn screen. Tests of adrenal function confirmed adrenal hypoplasia congenita and molecular evaluation revealed a novel missense NROB1 mutation. Replacement steroid therapy was promptly initiated, but he subsequently developed growth failure despite optimal nutritional and medical steroid therapy. Further biochemical analyses confirmed isolated idiopathic growth hormone deficiency.

Growth failure in adequately treated infants with adrenal hypoplasia congenita is rare and the role of DAX-1 in the development of pituitary somatotropes is not known. There is variable genotype-phenotype correlation in X-linked adrenal hypoplasia congenita but novel NROB1 missense mutations could offer insight into the function of the various DAX-1 ligand-binding domains.