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Liberman B; Nogueira KC; Huayllas MC; Goldman J; Cukiert A.
Departments of Endocrinology and Neurosurgery, Hospital Brigadeiro, Sao Paulo SP, Brazil
Introduction: The hypernatremia/hypodipsia syndrome is usually associated to well documented lesions involving the pituitary/hypothalamic region. We report on a patient with hypernatremia/hypodipsia syndrome in whom imaging of this region was negative.
Case Report: A 17 years-old young girl was first examined by the age of 10 years. She presented with hypodipsia, repetitive episodes of severe dehydration and irritability. By that time, her biochemical investigation showed sodium plasma level of 170mEq/L, BUN of 130 mg/dL, creatinine of 1.9 mg/dL and plasma and urinary osmolarity of 330 mosm/L and 916mosm/L, respectively. She had palatal cleft and mental retardation. She needed many in-patient periods when she presented with severe hypernatremia (up to 192 mEq/L) and variable alterations in the level of consciousness over the last 7 years. MRI of the head showed septum pelucidum agenesis and normal pituitary/hypothalamic region. A normal-looking neurohypophisis was clearly seen. During this period, she has continuously shown inability to additionally concentrate urine in spite of very high serum osmolarity and no diabetis insipidus. She is currently being treated with DDAVP 30ug/day and a special water intake program.
Discussion: The hypernatremia/hypodipsia syndrome is usually associated to discrete lesions located in the pituitary/hypothalamic region, such as tumors, aneurysms, granulomatous disease etc. In these patients, there is deficiency of AVP release related to the topography of the lesion. AVP concentration is usually low, but not absent and overt diabetis insipidus is rare. Diabetis insipidus may occur when there is complete destruction of the neurohypophisis. Patients presenting with functional hypernatremia /hypodipsia syndrome and normal anatomy of the pituitary/hypothalamic region are extremely rare. MRI of this region was normal in our patient but she presented with two distinct midline defects (palatal cleft and septum pelucidum agenesis). We postulate that functional abnormalities related to midline anatomical alterations not adequately documented by MRI are the cause of this syndrome in our patient.