A Rare Cause of Cushing's Syndrome: an Adrenocorticotropic Hormone (ACTH)-Secreting Pheochromocytoma.

Cushing's syndrome (CS) is a rare clinical entity that results from prolonged exposure to supraphysiological levels of glucocorticoids. It may result from adrenocorticotropic hormone (ACTH)-dependent or nondependent stimuli. In very rare cases, ACTH production does not derive from the pituitary gland but is of an ectopic origin. We present a case of a 51-year-old woman with cushingoid physical features, who was admitted to the emergency department with a hypertensive crisis, hyperglycemic state, and severe hypokalemia. During the diagnostic workup, the unequivocal confirmation of hypercortisolism status and ACTH elevation led to the suspicion of Cushing's disease. However, additional testing with a corticotropin-releasing hormone test and inferior petrosal sinus sampling suggested against this etiology. Surprisingly, a body computerized tomography scan incidentally revealed the presence of a left adrenal mass with a high uptake in a 68 Ga-DOTANOC positron emission tomography scan. The further investigation documented elevated urinary metanephrines and normetanephrines. The patient was referred for surgical resection of the adrenal gland, and the anatomopathological report revealed the diagnosis of ACTH-secreting pheochromocytoma without local invasion or malignant features. Diabetes mellitus, hypertension, hypokalemia, and cushingoid stigmata were remitted soon after surgery. ACTH-secreting pheochromocytomas are extremely rare causes of CS. This diagnosis demands a high level of clinical suspicion and should be equated in the presence of severe metabolic changes overlapping CS's physical features. The total reversal of metabolic and clinical symptoms after surgical resection highlights the need to remember this etiology when performing a CS workup.