Ectopic adrenal adenoma causing chronic Cushing's syndrome (CS) is a rare phenomenon. Diagnosis is usually made years after disease onset because of the insidious nature of the ectopic adrenal gland and because it overlaps with common symptoms, such as overweight and hypertension, in the general population (Kreitschmann-Andermahr et al., 2015). Here, we report the case of a 46-year-old male with a 15-year history of severe hypertension, facial plethora, and centripetal obesity. During treatment for herpes zoster, the patient presented with severe hypokalemia and flaccid paralysis, characteristic changes associated with CS. The serum cortisol level was elevated and baseline adrenocorticotrophic hormone (ACTH) was suppressed. After administration of the low-dose overnight dexamethasone suppression test, plasma cortisol was 38.9μg/dL. A contrast computed tomography (CT) scan revealed normal adrenal glands and significant tumor adjacent to the right renal hilum measuring ∼3.6×2.3cm. The tumor was removed through retroperitoneoscopy, and pathological examination confirmed adrenocortical adenoma and myelolipoma metaplasia. The serum potassium level gradually became normal after surgical removal of the mass. In the current report, we have reviewed the pertinent literature and highlighted the importance of considering ectopic adrenal adenoma in the differential diagnosis of chronic CS with nonspecific symptoms.