Severe metabolic alkalosis–a diagnostic dilemma

BACKGROUND: Cushing's syndrome due to ectopic ACTH secretion has been associated with many cancers; most commonly small cell carcinoma of the lung and bronchial carcinoid tumors. Usually, patients who confer this diagnosis have poor prognosis. CASE PRESENTATION: A 66-year-old female presented with worsening shortness of breath and weakness over three days. Initial laboratory derangements included severe hypokalemia and metabolic alkalosis. Treatment included high amounts of potassium chloride and acetazolamide. Imaging studies revealed anterior medial right upper lobe lung mass as well as suspicion for many liver metastases. Liver biopsy was sought and was positive for small cell carcinoma. CONCLUSION: We describe a case of severe metabolic alkalosis and hypokalemia in a patient with Cushing's syndrome due to ectopic ACTH secretion from small cell lung cancer. To our knowledge, this is the first case identified which exhibited such significant metabolic derangements in the form of serum and arterial blood bicarbonate. As prognosis is quite poor, we recommend swift diagnosis and management.