A Rare Manifestation of a Rare Disease: Ectopic Cushing’s Syndrome Secondary to Olfactory Neuroblastoma

Introduction: Olfactory Neuroblastoma (ONB) is a rare malignant Neuroendocrine tumour. It is rarely reported to cause Ectopic Cushing’s Syndrome (ECS). Here, we report a case of ECS secondary to ONB.
Case Description: A 40-year-old lady presented with right sided focal seizures complicated with status epilepticus. She was diagnosed with Diabetes Mellitus with severe hyperglycaemia three weeks prior to this admission and started on insulin therapy. Investigations revealed severe hypokalaemia. MRI brain showed no focal lesions but there was mucosal thickening in the paranasal sinuses. Other electrolytes and screening for infections were normal.
She didn’t have obvious clinical features of Cushing syndrome except generalized monomorphic acne, but further assessment confirmed the diagnosis of severe ACTH dependant Cushing syndrome. MRI pituitary was normal. CECT Chest, Abdomen and Pelvis showed only enlarged adrenal glands. PET/CT revealed FDG avid nasal polyp. Histology of nasal polyp revealed olfactory neuroblastoma. Staging imaging with MRI brain with sinuses and orbits confirmed stage C tumour with extension into ethmoid sinuses and part of the brain. She underwent endoscopic resection of the tumour and radiotherapy.
Conclusion: In a case of ECS, we should look beyond the thoracoabdominal region including Sino nasal cavity.