A lung disease or lung disease is any disease or disorder that occurs in the lungs or causes the lungs not to function properly. Lung diseases are one of the biggest problems for global health, and are the cause of approximately one out of every six deaths in the world.

There are three main types of lung disease:

Diseases of the respiratory tract: these diseases affect the ducts (air or respiratory tract) that carry oxygen and other gases in and out of the lungs. These diseases cause a narrowing or obstruction of the respiratory tract and include asthma, emphysema and chronic bronchitis.

Diseases of lung tissue: these diseases affect the structure of lung tissue. The scarring or inflammation of the tissue causes the lungs not to be able to fully expand (“restrictive lung disease”). This makes it harder for the lungs to inhale oxygen (oxygenation) and release carbon dioxide.

Diseases of the pulmonary circulation: these diseases affect the blood vessels in the lungs. They are caused by coagulation, scarring or inflammation of said vessels. These diseases affect the ability of the lungs to capture oxygen and release carbon dioxide and can also affect cardiac activity.