Ectopic adrenocorticotropic hormone (ACTH) syndrome is characterized by hypercortisolism with bilateral adrenocortical hyperplasia and hyperfunction due to the hypersecretion of non-pituitary ACTH-secreting tumor, which leads to Cushing’s syndrome. The gene discussed is POMC; the disease is Cushing syndrome due to macronodular adrenal hyperplasia.