A 4-month old child presented with facial malformations and severe hypernatremia. Hypernatremia was secondary to diabetes insipidus due to a disorder of ADH secretion, associated with cerebral malformations. Clofibrate treatment was ineffective. However, after the patient was treated by a low osmotic residue diet, an increased water-intake and hydrochlorothiazide, natremia became normal and growth resumed.