An ectopic Cushing's syndrome as a cause of severe refractory hypokalemia in the ICU

Background: Ectopic Cushing's syndrome is a very rare condition caused by an ACTH-secreting tumor outside the pituitary or adrenal glands, and the majority of these cases are encountered in the context of paraneoplastic syndromes. The ectopic source of ACTH secretion is not always obvious to detection and can be challenging. We report a rare case, in which a hidden ACTH-secreting carcinoid tumor of the lung caused a severe refractory hypokalemia, leading us to a race against time to locate the tumor.Case presentation: A 33-year-old young male was admitted to the ICU for the management of a severe hypokalemia, and complains from several months of depression, increased weight, disabling non-radiating dorsal lower back pain and refractory arterial hypertension. The physical examination immediately suggested a Cushing's syndrome. The 24-h cortisoluria confirmed hypercortisolism and the increased ACTH level was oriented towards ACTH-dependent Cushing's syndrome. Thereafter, a dexamethasone suppression test was negative, indicating in favor of ectopic ACTH secretion. The etiological assessment via imaging and isotopes revealed a solitary pulmonary nodule at the right lower lobe estimated at 18 mm, the resection and anatomopathological analysis of which led to the diagnosis of carcinoid pulmonary tumor, and resolved hypercortisolism and its complications.Conclusion: A delayed diagnosis of Cushing's syndrome result in a consequent morbi-mortality, mainly due to cardiovascular events. The optimal treatment for ectopic Cushing's syndrome is surgical resection, thus making the localization of the tumor a key element.