Emphysema is a lung disease that involves damage to the air sacs (alveoli). The air sacs are unable to completely deflate (hyperinflation) and are therefore unable to fill with fresh air to ensure adequate oxygen supply to the body. Cigarette smoking is the most common cause of emphysema. Tobacco smoke and other pollutants are thought to cause the release of chemicals from within the lungs that damage the walls of the air sacs. This damage becomes worse over time, affecting the exchange of oxygen and carbon dioxide in the lungs.
Sarcoidosis is a disease of unknown cause in which inflammation occurs in the lymph nodes, lungs, liver, eyes, skin, and/or other tissues. The cause of the disease is unknown. Tissue samples from affected organs show clusters of immune cells (macrophages, lymphocytes, and multinucleated giant cells). These clusters are called granulomas.
Possible causes include a hypersensitive response to some factor in the environment, a genetic predisposition, or an extreme immune response to infection. The incidence varies widely according to race and sex.
The disease is most common among North Americans of African heritage and Northern European Caucasians. Women of African heritage are affected more than men of African heritage. The onset of the disease usually occurs in people between 30 and 50 years old. Sarcoidosis is very rare in young children.
Pneumonia is an inflammation of the lungs caused by an infection. Many different organisms can cause it, including bacteria, viruses, and fungi. It is a common illness that affects millions of people each year in the United States. Pneumonia can range from mild to severe, even fatal. The severity depends on the type of organism causing pneumonia as well as your age and underlying health.
Tuberculosis can develop after inhaling droplets sprayed into the air from a cough or sneeze by someone infected with Mycobacterium tuberculosis. The disease is characterized by the development of granulomas (granular tumors) in the infected tissues.
The usual site of the disease is the lungs, but other organs may be involved. The primary stage of the infection is usually asymptomatic. In the United States, the majority of people will recover from primary TB infection without further evidence of the disease.
Pulmonary TB develops in the minority of people whose immune systems do not successfully contain the primary infection. The disease may occur within weeks after the primary infection, or it may lie dormant for years before causing disease.