Extreme Hyponatremia in an Infant with Congenital Adrenal Hypoplasia due to a Novel NR0B1 (DAX-1) Mutation

Abstract

Extreme hyponatremia (<105 mmol/l) has rarely been reported in infants. It is potentially life-threatening and requires intensive care treatment. We report on a male infant with absence of weight gain from birth to day 33 of life despite adequate nutrition. On admission serum sodium and potassium were 104 and 5.9 mmol/L respectively. The infant's physical status revealed dehydration, but normal activity with no apparent neurological, circulatory or respiratory impairment. Global adrenocortical insufficiency was diagnosed and treated with hormonal substitution in addition to intravenous application of fluid, glucose and electrolytes. The rise of serum sodium was carefully monitored and adjusted to a target rate of 0.5 mmol/L/h. X-linked adrenal hypoplasia congenita (X-AHC) was confirmed by the identification of a novel nonsense NR0B1 (DAX-1) mutation (W236X). X-AHC in infants may present as failure to thrive despite adequate nutrition. Extreme hyponatremia may be associated with little symptoms if developing slowly. Rehydration and slow correction of serum sodium with solutions containing less sodium than normal saline is essential.