A Rapidly Progressive Case of Ectopic Adrenocorticotropic Hormone (ACTH) Syndrome

BACKGROUND Adrenocorticotropic hormone (ACTH)-dependent Cushing's syndrome (CS) secondary to an ectopic source is an uncommon condition, accounting for 4-5% of all cases of CS. Refractory hypokalemia can be the presenting feature in patients with ectopic ACTH syndrome (EAS), and is seen in up to 80% of cases. EAS can be rapidly progressive and life-threatening without timely diagnosis and intervention. CASE REPORT We present a case of a 74-year-old White woman who first presented with hypokalemia, refractory to treatment with potassium supplementation and spironolactone. She progressively developed generalized weakness, recurrent falls, bleeding peptic ulcer disease, worsening congestive heart failure, and osteoporotic fracture. A laboratory workup showed hypokalemia, hypernatremia, and primary metabolic alkalosis with respiratory acidosis. Hormonal evaluation showed elevated ACTH, DHEA-S, 24-h urinary free cortisol, and unsuppressed cortisol following an 8 mg dexamethasone suppression test, suggestive of ACTH-dependent CS. CT chest, abdomen, and pelvis, and FDG/PET CT scan showed a 1.4 cm right lung nodule and bilateral adrenal enlargement, confirming the diagnosis of EAS, with a 1.4-cm lung nodule being the likely source of ectopic ACTH secretion. Due to the patient's advanced age, comorbid conditions, and inability to attend to further evaluation and treatment, her family decided to pursue palliative and hospice care. CONCLUSIONS This case illustrates that EAS is a challenging condition and requires a multidisciplinary approach in diagnosis and management, which can be very difficult in resource-limited areas. In addition, a delay in diagnosis and management often results in rapid deterioration of clinical status.