We describe a 71-year-old woman with spontaneous rupture of the left pulmonary artery. She was admitted with pulselessness of her left arm and lack of sensibility in her left arm and leg. Echocardiography and thoracic CT did not confirm aortic dissection. CT only showed hematoma around the descending aorta. She underwent left-sided thoracotomy. Intraoperatively, a rupture of the left pulmonary artery without any evidence of an aneurysm was found. Potentially predisposing factors for this rupture were long-term use of steroids due to COPD and her age.