An Endocrine Picture In Disguise: A Progressive Olfactory Neuroblastoma Complicated With Ectopic Cushing Syndrome

ABSTRACT Objective: To describe a unique case of a 61-year-old patient presenting with ectopic Cushing syndrome as a paraneoplastic phenomenon due to adrenocorticotropic hormone (ACTH)-secreting bone metastasis of an olfactory neuroblastoma (ON). Methods: We report a detailed case, with clinical, biochemical, and imaging findings and compare it with existing literature. Results: A patient with an ON, with subsequent 10-year stable disease after initial craniofacial surgery, presented with paraparesis due to progressively metastasized ON disease located in the thoracic spine. During palliative chemotherapy, severe hypokalemia and muscle weakness developed, being part of paraneoplastic Cushing syndrome. Examination showed that metastatic bone lesions were mostly responsible for the ectopic secretion of ACTH, with just a few ACTH-secreting tumor cells located in the primary tumor. She was treated with a combination of ketoconazole and metyrapone that controlled cortisol levels. However, low potassium levels persisted. Finally, she underwent a bilateral adrenal resection, after which most cushingoid symptoms disappeared. She died 1 month later. Conclusion: Our case shows a growing ON with several bone metastases, which is a rare clinical condition. Moreover, this is the first report that ON is associated with bone metastases that express excessive ACTH secretion (and suggesting dedifferentiation of the primary tumor during chemotherapy treatment). Ectopic Cushing syndrome (with ACTH secreted by ON bone metastasis) can present late in the clinical trajectory. Finally, a bilateral adrenalectomy was needed to correct the life-threatening hypokalemia as part of the ectopic Cushing syndrome. Abbreviations: ACTH adrenocorticotropic hormone; CRH corticotropin-releasing hormone; IPSS inferior petrosal sinus smapling; ON olfactory neuroblastoma