Hypokalemia due to ectopic adrenocorticotropic hormone secondary to metastatic lung carcinoma

A 58-year-old man with diabetes mellitus and a history of chronic smoking presented with a 3-month history of lower back pain followed by lower limb weakness, uncontrolled blood glucose, and hypertension for the last 1 month. On physical examination, he had palpable right supraclavicular lymph nodes and hypertension. Arterial blood gas analysis showed metabolic alkalosis (pH, 7.56; partial pressure of carbon dioxide, 36 mm Hg; HCO3, 36 mmol/L). Blood biochemistry revealed severe hypokalemia (2.15 mEq/L) with normal creatinine (0.65 mg/dl) and calcium (9.3 mg/dl).