Edematous Hyponatremia Treated with Tolvaptan in a Patient with Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) patients rarely present with either syndrome of inappropriate antidiuretic hormone secretion or generalized edema. Tolvaptan is a selective vasopressin V2 receptor antagonist that produces effective aquaresis, and its use in ALS patients has not been previously reported. A 50-year-old male ALS patient was admitted because of both generalized edema and dilutional hyponatremia. These manifestations were refractory to conventional diuretics and fluid therapy, but a very brisk diuresis was induced by tolvaptan administration. Edema and hyponatremia were also improved, and the patient was able to be discharged without tolvaptan. In this case report, we postulate how edema and dilutional hyponatremia developed in the patient, and discuss the mechanism of tolvaptan in treating hypervolemic hyponatremia. Further experience is necessary to evaluate the usefulness of tolvaptan in patients with neurological disorders.