TY - JOUR T1 - Olfactory neurocytoma as a unique cause of chronic SIADH JF - BMJ Case Reports JO - BMJ Case Reports DO - 10.1136/bcr-2020-235021 VL - 14 IS - 1 SP - e235021 AU - Mohammad Farwana AU - Chrysostomos Tornari AU - Ann Sandison AU - Pavol Surda Y1 - 2021/01/01 UR - http://casereports.bmj.com/content/14/1/e235021.abstract N2 - A 32-year-old man was found to have a nasal mass on DOTATATE positron emission tomography (PET) scan to investigate the cause of his syndrome of inappropriate antidiuretic hormone secretion (SIADH). The patient presented 6 years earlier with malignant hypertension followed by a second emergency admission for hyponatraemia. Multiple scans and blood tests over 6 years yielded no cause for his SIADH. Nasendoscopy was unremarkable. A PET scan prompted endoscopic sinus surgery which resulted in the resection of a mass in the anterior hiatus semilunaris. The histological findings were fitting with a diagnosis of a neurocytic-type tumour favouring an olfactory neurocytoma. Following resection, the patient remains well and is cured of his SIADH. An olfactory neurocytoma although rare should be considered as a benign differential for a mass in the nasal space. This case demonstrates how an olfactory neurocytoma can present as a cause of SIADH. ER -