Idiopathic central diabetes insipidus

Idiopathic central diabetes insipidus (CDI) is a rare disorder characterized clinically by polyuria and polydipsia, and an abnormal urinary concentration without any identified etiology. Two young adults with abrupt onset of polydipsia, polyuria, and excessive thirst sought our attention. None had neurological deficits or a family history of diabetes insipidus. Low urine osmolality persisted despite water deprivation and urine osmolality increased dramatically after the deamino-D-arginine-8-vasopressin (dDAVP) test, observations consistent with the diagnosis of CDI. Anterior pituitary dysfunction was absent. Magnetic resonance imaging (MRI) of the brains of both cases showed normal anatomical structures, except for the absence of a normal hyperintense signal in the posterior pituitary. Secondary causes of CDI including trauma, infection, autoimmunity, and infiltrative disorders were excluded. Genetic analysis also revealed no mutations in the arginine vasopressin-neurophysin II gene. After dDAVP administration via nasal spray, their symptoms related to CDI were completely resolved. The brain MRI at regular follow-up remained unchanged for 3 years. Exclusion of organic brain disease and the absence of mutations in the gene encoding arginine vasopressin are essential for the diagnosis of idiopathic CDI.