Hyponatremia secondary to olfactory neuroblastoma.

A patient with a four-year history of unexplained hyponatremia was seen with recurrent nasal discharge and was found to have a typical olfactory neuroblastoma. The clinical laboratory diagnostic studies suggested that the patient's sodium deficiency was secondary to the syndrome of inappropriate antidiuretic hormone. Subsequent resection of the neoplasm led to resolution of the hyponatremia, suggesting that a (tumor-associated) humoral factor, such as vasopressin or a vasopressinlike substance, was responsible for the electrolyte disturbance. A search of the literature disclosed one previous case of vasopressin-secreting nasal neuroblastoma.