The syndrome of the ectopic production of the adrenocorticotropic hormone (ACTH) presents a version of endogenous hypercorticism which is the most challenging one for diagnostics and treatment. The paper discusses a clinical case of the ACTH-ectopic syndrome diagnosed in an elderly female patient. Advanced age and ongoing long-term treatment may obscure the typical manifestations of a disease. At the same time, it is common for doctors to be less focused on identifying rare diseases when working with elderly patients. A combination of clinical signs (resistance to the antihypertensive therapy; poorly controlled glycemia; increasing weakness; hypokalemia and severe skin pigmentation) allowed for suspecting symptomatic hypertension. Doctors need to be alert and to identify rare diseases among patients of any age group. This case also demonstrates the productivity of a multidisciplinary approach (a team including cardiologists, endocrinologists, radiology specialists and surgeons).