Abstract: FR-PO0888
Hypodipsia and Hypernatremia: A "RERE" Genetic Syndrome
Session Information
- Fluid, Electrolyte, and Acid-Base Disorders: Case Reports - 1
October 23, 2026 | Location: Exhibit Hall A, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Fluid, Electrolytes, and Acid-Base Disorders
- 1102 Fluid, Electrolyte, and Acid-Base Disorders: Clinical
Authors
- Nevin, Connor William, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States
- Monk, Brian Christopher, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States
- Hladik, Gerald A., The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States
Introduction
Chronic hypernatremia due to hypodipsia is a rare syndrome. The evaluation begins with an assessment of volume status, fluid intake, and urinary volume/indices. Low urine volume and hypodipsia may be due to congenital or acquired hypothalamic lesions.
Case Description
A 29-year-old male with developmental delay, frontal bossing, cleft palate, and right eye blindness due to phthisis bulbi was admitted for evaluation of a serum Na level of 176 mEq/L after presenting with right arm and leg weakness.
His serum Na was consistently elevated in the ~150 range for at least 6 years. The patient’s family reported that he had limited fluid and nutritional intake that had worsened 1 week prior to admission. He did not have diarrhea, vomiting, inadequate access to water, or polyuria. Urinary osmolality was 1155 mOsm/kg and urine Na was 142. Brain MRI showed a 1.2 cm pituitary adenoma and thickened stalk. He was treated with D5W and his weakness resolved as his serum Na returned to baseline levels. Copeptin (CT-proAVP) level was elevated at 26.3 pmol/L (<13.1).
Discussion
The differential diagnosis of hypernatremia includes hypotonic fluid losses or inadequate water intake. Hypotonic fluid losses in the urine due to arginine vasopressin deficiency or resistance are manifest with polyuria and diluted urine, whereas hypodipsia or hypotonic GI fluid losses present with low urinary output and concentrated urine. This patient’s urine osmolality exceeded 700 mOsm/kg indicating adequate AVP production confirmed by the elevated copeptin level. Urine Na levels are generally <25 when there is hypotonic fluid loss and hypovolemia. However, this patient’s urine Na level was quite high, consistent with hypodipsic hypernatremia. The thickened pituitary stalk seen on MRI points toward a structural lesion of the hypothalamus.
The presence of hypospadias, developmental delay, cleft palate, and right eye blindness suggested a congenital disorder such as Neurodevelopmental disorder with or without anomalies of the brain, eye, or heart (NEDBEH) due to a pathogenic variant in the RERE gene. Other potential causes include inflammatory or infiltrative hypothalamic disease such as sarcoidosis or IgG4-related disease.
Treatment is focused on facilitating adequate water intake through timed water intake and behavior modification.
In summary, hypodipsia is a rare cause of hypernatremia that has a broad differential diagnosis that requires careful systematic investigation.