Ectopic ACTH Syndrome Caused by Pheochromocytoma: A Case Report and Systematic Review

Ectopic adrenocorticotropic hormone (ACTH) syndrome caused by pheochromocytoma is extremely rare, and its highly variable clinical manifestations make diagnosis challenging.

This report describes a case of a 48-year-old female with typical Cushingoid features who complained of edema in both lower limbs for 20 days. Laboratory testing showed hypokalemia with metabolic alkalosis, high levels of cortisol and ACTH, and the absence of circadian rhythm. Neither low-dose or high-dose dexamethasone suppression testing could inhibit cortisol secretion. Abdominal computed tomography showed a 32-mm mass in the left adrenal gland and hyperplasia of the right adrenal gland. The patient underwent resection of the left-sided adrenal adenoma, and pathological examination revealed features of a pheochromocytoma. Immunohistochemistry showed positivity for chromogranin A, synaptophysin, neuron-specific enolase, and ACTH, with a Ki67 labeling index of approximately 1%. Post-operatively, the patient's electrolyte, serum cortisol, and ACTH levels returned to normal rapidly, and the symptoms of edema resolved. The diagnosis was ectopic ACTH syndrome caused by pheochromocytoma.

Based on this case and the presented literature review, we recommend that all patients with an elevated ACTH level and adrenal mass be screened for ectopic ACTH syndrome caused by pheochromocytoma.