Pleural disease is the general name given to several distinct diseases of the pleura, the thin membranes that cover the lungs and line the chest cavity. Often caused by asbestos exposure, pleural disease can also be caused by factors such as infection, inflammation, injury and certain medications.

Like asbestosis, asbestos-related pleural disease is the result of scarring. The primary distinction between these two conditions is the location of the scarring. Asbestosis occurs in the lungs themselves, while pleural disease occurs in the lining surrounding them. For reasons not yet clear, asbestos exposure is more likely to lead to higher accumulations of asbestos in some areas of the pleura than in the lungs. Pleural disease is now recognized as the most common indicator of asbestos exposure.

Although the symptoms of asbestos-related pleural disease are treatable, the disease itself has no known cure. Pleural disease may go undetected until 10 to 20 years or more after asbestos exposure. Meanwhile, the asbestos continues to cause irritation and scarring, and the disease progresses.

Types of Pleural Disease

In addition to pleural mesothelioma, which is a malignant disease, there are several benign forms of asbestos-related pleural disease. These include:

• pleural plaques and calcification
• pleural thickening
• pleural effusion

Pleural Effusion

Pleural effusion is defined as an abnormal build-up of fluid in the pleural space between the lung and the pleural lining. Diagnosing benign asbestos-related pleural effusions can be a challenge because they may be difficult to distinguish from effusions caused by mesothelioma. There is no evidence, however, to indicate that benign pleural effusions lead to mesothelioma.

Symptoms of pleural effusion may include shortness of breath, chest pain, fever, and swelling in the legs. In some cases, there may be no symptoms at all. Benign pleural effusions are treatable, with efforts directed at removing the fluid and preventing it from accumulating again.

Pleural Plaques and Calcification

Pleural plaques are small, hard surfaces that form on the pleura, comparable to the arteriosclerotic plaques that may form in coronary arteries. They are the most common (and often the only) form of pleural disease associated with asbestos exposure. The plaques are typically discovered only many years after the exposure.

While pleural plaques themselves are neither malignant nor considered to be premalignant, they do indicate exposure to asbestos. Therefore, pleural plaques represent an increased risk for mesothelioma and other asbestos-related diseases. In all, approximately 60 percent of workers exposed to asbestos will develop pleural plaques. Pleural plaques rarely cause breathing difficulties or other disabling symptoms.

More defined than pleural thickening, pleural plaques may become calcified over time. These calcifications are hard calcium deposits, which produce dense images on x-ray.

Pleural Thickening

When scarring is more diffuse than the local scarring seen in pleural plaques and extends along the chest wall, it is known as pleural thickening. This thickening may limit expansion and contraction of the lungs, often resulting in breathing problems. Like plaques, pleural thickening indicates exposure to asbestos and increases the risk for more serious asbestos-related diseases. However, pleural thickening is less common than pleural plaques.

Patients with pleural thickening or pleural plaques may be advised to have annual screenings for lung cancer and other serious forms of lung disease.

Resources

http://www.fccc.edu/cancer/types/lung/pleural.html

http://www.medscape.com/viewarticle/460443

http://www.asbestosnetwork.com/health/he_asbestosis.htm

http://www.merck.com/mmpe/sec05/ch057/ch057c.html

http://www.ncbi.nlm.nih.gov/pubmed/9646983

http://www.eoearth.org/article/Asbestos_health_hazards