Case Presentation: A 34-year-old woman presented with rapidly progressing clinical signs/symptoms of Cushing’s syndrome and demonstrated marked hypercortisolism (cortisol 2428 nmol/L; ACTH 163 ng/mL; urinary free cortisol 815 μg/24 h; K+ 2.4 mmol/L). The gene discussed is POMC; the disease is Cushing syndrome.