Pleural Thickening and Asbestos

Pleural thickening, also known as diffuse pleural thickening (DPT), is a lung disease in which extensive scarring thickens the pleura, the thin membrane that covers the lungs. As the scar tissue grows, it can encase the lung and close off the space between the lungs and pleura. The condition, one of the most commonly diagnosed signs of asbestos exposure, may cause chest pain and a significant decline in breathing function.

Although the cause and severity of the condition can vary, it is often the result of prolonged exposure to asbestos. When we inhale asbestos fibers, they can become embedded in the pleura. There, the fibers can trigger an inflammatory response that causes the progressive buildup of fibrous scar tissue.

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Pleural thickening does not always signify an asbestos-related disease, however. A number of other diseases can cause the disease, including:

  • Empyema – an accumulation of pus in the pleural space

  • Hemothorax – an accumulation of blood in the pleural space

  • Fibrinous pleuritis – a type of pleural inflammation

  • Pulmonary embolism – the blockage of a main artery to the lungs

Pleural thickening should not be confused with pleural plaques, another condition that can precede the formation of an asbestos-related cancer. Pleural plaques are firm, sometimes calcified lesions of scar tissue that grow in discrete patches on the pleura.

Plaques may coexist with pleural thickening, but they feature much less extensive scarring and cause minimal, if any, lung impairment. Pleural thickening typically originates on the visceral layer of the pleura, which lines the lungs, while plaques often arise on the parietal pleura, which lines the rib cage. Pleural thickening commonly occurs after a patient suffers pleural effusion, an excessive buildup of fluid in the pleural space.

Symptoms

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In its earliest stages, the condition has no symptoms. As the disease progresses, patients may experience chest pain and breathlessness. In one study involving patients with moderate to severe pleural thickening, 95.5 percent complained of breathlessness, 65 percent described moderate breathlessness, and 11 percent described severe breathlessness.

It can also cause restrictive lung disease, which prevents the lungs from fully expanding. As a result, patients experience decreased lung volume and may have to work harder to breathe. One case report associates pleural thickening with severe restrictive lung disease that led to respiratory failure and death.

Diagnostic Process and Mesothelioma

Studies involving asbestos-exposed workers have shown that pleural thickening occurs in 5 to 13.5 percent of workers between 3 and 34 years after their initial exposure to asbestos. The condition can arise within a year of exposure, but it most commonly takes 15 to 20 years before doctors make a diagnosis.

There are a number of tests that doctors can use to diagnose the condition. On an imaging scan of the chest, pleural thickening appears as an irregular shadow on the pleura that extends over at least 25 percent of the chest wall.

CT Scans

The condition is most commonly diagnosed via chest X-ray, but diagnosis by (computed tomography CT scan) is becoming increasingly popular. Numerous studies have established that when compared to X-rays, high resolution CT scans can better detect pleural thickening, pleural plaques and asbestosis. CT scans can detect early signs of pleural thickening, when scar tissue is between 1 and 2 mm in thickness.

PET Scans

In some cases, doctors perform a positron emission tomography scan (PET scan) to distinguish between pleural thickening and pleural mesothelioma, which can affect patients simultaneously. The presence of pleural thickening is not enough to confirm a mesothelioma diagnosis, but it can be a sign of significant asbestos exposure and promotes early detection.

Doctors may be able to provide an early diagnosis for mesothelioma patients with the simultaneous use of PET and CT scans. Catching mesothelioma in its earliest stages can lead to a better prognosis and a wider range of treatment options.

Treatment

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While the damage is irreversible, there are some treatment options available. Most commonly, doctors offer therapies to treat the disease's symptoms. They can prescribe pain medications such as bronchodilators, steroids and antibiotics that make breathing easier.

When a patient is experiencing pleural effusion, a reoccurring condition that often precedes pleural thickening, doctors can perform a thoracentesis to remove excess fluid and alleviate pressure in the chest.

Smoking can lead to decreased lung function, so health care professionals recommend that patients stop smoking if diagnosed with pleural thickening. By quitting, patients may also reduce their risk of developing more serious lung diseases.

Although for the most part treatment is limited to supportive and symptomatic care, rare case reports have shown pleurectomy surgery to be effective in some progressive cases. This aggressive treatment, usually reserved for patients with pleural mesothelioma, involves removal of parts of the pleura and other nearby linings of the chest.

Additional Resources

  1. Miles, S., Sandrini, A., Johnson, A. and Yates, D. (2008, September 8). Clinical Consequences of Asbestos-related Diffuse Pleural Thickening: A Review. Journal of Occupational Medicine and Toxicology. Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2553409/
  2. Myers, R. (2012, July). Asbestos-related Pleural Disease. Retrieved from http://www.eoncology.eu/site/wp-content/uploads/2013/01/Asbestos-related-pleural-disease.pdf
  3. Baldi, Alfonso. Mesothelioma from Bench Side to Clinic. Nova Science Publishers: New York. 2008.
  4. O'Byrne, K., Rusch, V. Malignant Mesothelioma. Oxford University Press: New York. 2006.
  5. Pass, H., Vogelzang, N. and Carbone, M. Malignant Mesothelioma: Advances in Pathogenesis, Diagnosis, and Transitional Therapies. Springer: 2005.

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