Ectopic Adrenocorticotropic Hormone Syndrome in a Patient Diagnosed With Lung Adenocarcinoma and Hospitalized Due to Diabetic Ketonuria: A Case Report.

Ectopic adrenocorticotropic hormone (ACTH) syndrome (EAS) is most often a paraneoplastic manifestation of small-cell lung cancer and is rare in lung adenocarcinoma. Its features include a cushingoid appearance, skin hyperpigmentation, muscle weakness, hypertension, glucose intolerance, hypokalemia, and metabolic alkalosis resulting from nonsuppressible, ACTH-driven hypercortisolism. We report a 70-year-old man admitted with pneumonia and diabetic ketonuria without acidosis, in whom EAS secondary to a poorly differentiated lung adenocarcinoma was diagnosed. Key biochemical findings were a markedly elevated 8 a.m. plasma ACTH (149.3 pg/mL), grossly elevated serum cortisol (54.94 μg/dL) with loss of diurnal rhythm, elevated 24-h urinary free cortisol, and failure of cortisol suppression after both low- and high-dose dexamethasone, with a normal pituitary MRI-a profile consistent with an ectopic ACTH source. What distinguishes this case is that the heralding presentation was a refractory metabolic emergency (hyperglycemia with diabetic ketonuria; HbA1c 6.3%, indicating no pre-existing poorly controlled diabetes) rather than the classic cushingoid phenotype. The patient deteriorated rapidly and died on the third day after CT-guided lung biopsy, before tumor-directed therapy or confirmatory ACTH immunohistochemistry could be undertaken. This case highlights that EAS from lung adenocarcinoma may present primarily as a severe metabolic emergency and that early biochemical screening and control of hypercortisolism are critical.