SUN-375 A Diagnostic and Therapeutic Challenging Case of Ectopic Cushing Syndrome

Introduction: Ectopic ACTH secretion is a rare cause of ACTH dependent Cushing syndrome and accounts for approximately 10% of the cases. Identification of ectopic source involves a complex evaluation. We present a case of ectopic Cushing syndrome from small cell cancer posing diagnostic and therapeutic challenges. Clinical case: A 50-year-old woman with HTN, newly diagnosed DM, 45 pack year smoking admitted to hospital for pneumonia, uncontrolled HTN, and hypokalemia. The patient’s CT chest and abdomen showed a new 2cm cavitary lesion in the right lung and incidental left adrenal nodule. Biopsy of the cavitary lesion was negative for malignancy. Endocrinology was consulted for left adrenal incidentaloma. The patient reported 40lb weight gain in 6 months, hirsutism, proximal muscle weakness, and easy bruising. On physical exam, facial plethora, thinning scalp hair, supraclavicular fullness, diffuse bruising, truncal obesity, and bilateral pedal edema were noted. Bilateral lower extremities strength was markedly decreased. No abdominal purple striae were present. Work up for Cushing's showed, serum cortisol after 1mg overnight Dexamethasone suppression test- 49.3mcg/dl (N<1.8), 24 hour urine free cortisol-5767mcg/dl (N<45), midnight salivary cortisol 3.47mcg/dl (N<0.01-0.09) and ACTH-183pg/ml (6-58). 8mg Dexamethasone suppression test did not suppress cortisol more than 50%. Work up for Pheochromocytoma and Aldosteronism were negative. Labs confirmed ACTH dependent Cushing's. The pituitary MRI was unremarkable. Octreotide scan was negative. Ga- DOTATATE scan was unavailable. Meanwhile, the patient deteriorated within a few days, developed right lung empyema, shingles, and could not ambulate without support. The patient was started on Ketoconazole and later switched to Metyrapone because of insurance. The patient had bronchoscopy for her unresolved empyema, which revealed small cell lung cancer in the brushings. Post-discharge, the patient responded fairly well to chemo and radiation. But her cortisol was not fully controlled with ketoconazole, then Metyrapone. And she required high doses of potassium. The complications of her ectopic Cushing's became more life threating necessitating referral for bilateral adrenalectomy for definitive management of her ectopic Cushing's. Conclusion: Localization of ectopic source of ACTH secretion poses a diagnostic challenge. In our case, the initial biopsy of cavitary lung lesion was negative, and later ectopic source was identified on bronchial washings. Early diagnosis of the ectopic source is crucial to avoid complications from Cushing's. Even if initial localization fails, it is prudent to start medical management as early as possible for hypercortisolemia as in our case and to refer for bilateral adrenalectomy if uncontrolled, to decrease the morbidity and mortality from Cushing's.