Adipsic Hypernatremic Myopathy

Chronic hypernatremia due to a defect in thirst mechanism or in osmoregulation of arginine vasopressin secretion is very rare.1 Chronic hypernatremia due to a selective defect in osmoregulation of thirst could be secondary to structural lesion in hypothalamus such as tumor, cyst, or granulomas, and less commonly without demonstrable structural lesions.2 This is often asymptomatic but may present with neurologic signs such as delirium, lethargy, and less commonly, muscle weakness.3 We report a patient who presented with muscle weakness and rhabdomyolysis due to an isolated defect in osmoregulation of thirst without evidence of a structural lesion.