Esthesioneuroblastoma presenting as syndrome of inappropriate antidiuretic hormone secretion.

Hyponatremia is the most common fluid electrolyte disorder in hospitalized patients. Syndrome of inappropriate antidiuretic hormone secretion (SIADH) is the main cause of normovolemic hyponatremia, it can be caused by diverse etiologies: malignant tumors are the most feared cause that clinician persists in finding. Exceptionally, SIADH can complicate Esthesioneuroblastoma (ENB) or olfactory neuroblastoma, a rare tumor of the nasal sinus cavities.