Emphysema is a lung disease that damages the air sacs in the lungs called alveoli, reducing the ability to expel air. It is most often caused by cigarette smoking, which damages lung tissues over many years. While there is no cure for emphysema, treatments can help slow its progression by managing symptoms and avoiding further lung damage from smoking or air pollution. Physical exams are used to diagnose emphysema based on a patient's medical history and symptoms like shortness of breath.