WHAT CAUSES PLEURAL THICKENING? SYMPTOMS, DIAGNOSIS, LATEST IN TREATMENT

Medically Reviewed by Dr. Rae Osborn, Ph.D. and Updated on July 25, 2024

Pleural thickening is a lung ailment affecting the pleura, the thin membrane lining the chest cavity and covering the lungs. The pleura has two layers: the visceral pleura that adheres to the lung surface and the parietal pleura that attaches to the chest wall. Between these layers resides the pleural space, which is filled with fluid that assists with making the pleural layers mobile. The pleura helps the lungs move smoothly during breathing and also protects them from infections and injuries.^[1]

Sometimes, the pleura becomes inflamed, scarred, or fibrous due to infections, chest injuries, and other health conditions. This can lead to thickening of the pleura, which narrows the pleural space and impairs lung function. Pleural thickening can give rise to chest pain, breathlessness, and other symptoms. Pleural thickening also often occurs in patients who have Mesothelioma, a rare and aggressive cancer of the pleura.^[2]

In this blog, we will explain the common types and causes of pleural thickening, alongside symptoms, diagnosis, treatment, and prevention. The prognosis of pleural thickening and how it relates to mesothelioma are also discussed.

Pleural Thickening Symptoms

The symptoms of pleural thickening make the condition quite difficult to miss. The two giveaway symptoms are:

• Pain or discomfort that is felt in the chest, especially when breathing, coughing, or moving
• Breathlessness or difficulty with breathing that intensifies during physical activity or exertion

During pleural thickening, the pleura are enlarged and thickened due to scar tissue^[3], and rub against one another, contributing to irritation as well as airway constriction. This is why the condition often gives rise to chest pain and breathlessness.

If left to go on for too long without adequate treatment or drainage, pleural thickening may result in the following complications:

• Reduced lung capacity: Loss of lung tissue, elasticity, or restricted lung expansion can lower the amount of air that the lungs can hold, resulting in lower oxygen levels and higher carbon dioxide levels in the blood.
• Increased risk of pleural effusion: Pleural effusion is a condition where excess fluid accumulates in the pleural space, causing more pressure on the lungs and impairing their function.
• Rounded atelectasis^[4]: This is when the lung is partially collapsed.

When complications are present, they may be accompanied by additional symptoms, including a persistent cough, fever, fatigue, weight loss, dizziness or lower ability to think, and a decreased tolerance to exercise or physical activity.

Types and Causes of Pleural Thickening

Pleural thickening can be caused by various factors that can damage or irritate the pleura. The most common ones include:

• Asbestos exposure and Mesothelioma: This is one of the most common and serious causes of pleural thickening. Mineral fibers like asbestos were once widely used for flooring, roofing, insulation, and other applications. It releases tiny, toxic fibers into the air that can get lodged in the lungs and the pleura, causing inflammation, scarring, and thickening. Asbestos exposure is also a prime cause of mesothelioma. Mesothelioma, a rare and aggressive cancer of the pleura, is capable of spreading to other organs, such as the lungs, heart, or abdomen. Commonly caused by asbestos exposure, it can damage pleural cell DNA, resulting in abnormal and uncontrollable growth. While banned or regulated in many countries, asbestos can still be found in some old buildings or products. 
• Infections: When the lungs or the pleura are infected, it leads to inflammation, fluid accumulation, and thickening. Some of the common infections that can cause pleural thickening are tuberculosis, pneumonia, bronchitis, and pleurisy.
• Lung diseases: Lung diseases are often a source of chronic inflammation that can affect the pleura, causing scarring or fibrosis and leading to pleural thickening. Interstitial lung disease (ILD) and chronic obstructive pulmonary disease (COPD) are two prevalent lung conditions that lead to pleural thickening.
• Chest injuries: Damage to the chest wall or lungs can lead to bleeding, bruising, puncture, and ultimately pleural thickening. Common chest injuries associated with pleural thickening include rib fractures, gunshot wounds, and stab wounds. While not thought of as a chest injury, chest surgeries can also cause pleural thickening.

Pleural thickening is classified into four main types depending on its location around the lungs, whether it affects both sides (bilateral) or only one side (unilateral), and how it looks on imaging tests such as x-rays or CT scans.

Types of pleural thickening are summarized in the following table:

Pleural Thickening Diagnosis

To diagnose pleural thickening, a doctor will assess the patient’s symptoms with a physical examination and take a thorough medical history. During the examination, they will likely need to listen to the patient’s chest and check their vitals. They may ask about whether there is a history of respiratory disease or cancer in the family or whether the patient had any chest injuries in the past. This will help them to assess the possible causes of the patient’s respiratory symptoms.

To aid the diagnosis, doctors will make use of imaging tests, which may or may not be a service they offer their patients. Imaging tests used to detect and assess pleural thickening include:

• Chest X-ray: X-rays are simple, quick, and able to generate an image of the lungs, heart, and ribs. They can detect the presence, extent, and pattern of the pleural thickening, as well as any fluid accumulation or other abnormalities in the chest.
• CT scan: This is a more detailed and advanced test that uses a series of X-rays to create a three-dimensional image of the chest, revealing more detail inside the lungs, such as blood vessels. CT scanning can provide more information about pleural thickening, such as its density, shape, and location, as well as any nodules, tumors, or other complications.
• Magnetic resonance imaging (MRI): This is another imaging test that can help detect pleural thickening.^[5]
• Biopsy: A small sample of pleural tissue is taken for a biopsy, and it is examined under a microscope. It is usually used to confirm whether pleural thickening is caused by a malignancy or not.

Pleural Thickening Treatment Options

Most cases of pleural thickening are regarded as lifelong conditions that increase one’s susceptibility to respiratory diseases and malignancy. This is especially true in cases of pleural scarring. Treatment options revolve around managing symptoms, treating underlying infections, draining excessive fluids in the case of pleural effusion, or surgical removal of pleural growths or plaques.

Some of the available treatments include:

Medication: Medication can be used to treat mild to moderate cases of pleural thickening. Common medications administered for managing pleural thickening include steroids, anti-inflammatories, painkillers, bronchodilators, or antibiotics (if appropriate).

Pleural catheter: This option involves the insertion of a thin tube into the pleural space to drain the excess fluid and relieve the pressure on the lungs. The catheter can be left in place for a long time, and the fluid can be drained at home or in a clinic. The pleural catheter can be used as a palliative treatment for patients who are not suitable for surgery or pleurodesis.

Pleurodesis: This option involves the injection of a chemical or a drug into the pleural space to create an artificial adhesion between the two layers of the pleura. This can prevent the recurrence of pleural effusion and reduce the symptoms of pleural thickening. Pleurodesis can be performed through a thoracentesis (a needle insertion into the pleural space) or a thoracoscopy.^[6]

Pleurectomy with decortication: This is a surgical procedure that involves removing the affected pleura and any visible tumor from the chest wall and lung.^[7] Pleurectomy is performed through a thoracotomy (a large incision in the chest) or a thoracoscopy (a minimally invasive procedure using a thin tube with a camera and instruments). It can help to relieve the pressure on the lung and improve its function. 

• Mortality Risk. A recent study warns against opting for pleurectomy with decortication, as it was associated with a 28% increased risk of death compared to chemotherapy alone in patients with malignant pleural mesothelioma.^[8]

Latest Advances in the Treatment of Pleural Thickening

There are not that many advances solely with regard to pleural thickening treatments, as most research efforts are geared toward treating mesothelioma.

Two promising therapies that may become widely available to help patients who have pleural thickening in the future include:

• Intrapleural fibrinolytic therapy: It can be used to enhance the outcomes for pleural drainage and pleurodesis, lower the need for surgery^[9], help restore the normal movement of the lung, and reduce the symptoms of pleural thickening. A recent study found that intrapleural fibrinolytic therapy was effective and safe for patients with pleural infection, a common cause of pleural thickening.^[10] There are several variations of this therapy currently undergoing phase I and II clinical trials.
• Mesenchymal stem cell therapy: This is a treatment that involves transplanting stem cells into the pleural space to regenerate the damaged pleura and lung tissue. It might help to prevent pleural thickening caused by fibrosis or scarring and improve lung function. Specialized cell therapies, such as using NK cells, are being developed for those with Mesothelioma, which can help the immune system better target and remove the tumor.^[11]

These are some of the promising treatments that are being developed and tested for pleural thickening. However, more research is needed to confirm their efficacy and safety in humans.

If you have pleural thickening, you should consult your doctor about the best treatment options for your condition.

Prognosis of Pleural Thickening

The prognosis of pleural thickening depends on various factors, such as age, health, cause, and severity of the condition. According to some studies, the average life expectancy of patients with pleural thickening is about 10 to 15 years, depending on the factors mentioned above. However, this is only a general estimate, and the actual life expectancy of each patient may vary widely, depending on their individual situation and response to treatment. For instance, a patient with malignant pleural mesothelioma may have a life expectancy of only 12 months.

Some of the factors that influence the prognosis of pleural thickening are:

• Age: Patients who are older typically have an unfavorable prognosis as they may have a lower tolerance towards treatment as well as comorbidities, such as heart disease, that can affect their lung function and overall health.
• Malignancy: Those with mesothelioma tend to have a poorer prognosis.
• Severity: Patients who have a mild or moderate degree of pleural thickening tend to have a better prognosis than patients who have severe or extensive pleural thickening.

Tips for Prevention of Pleural Thickening

The prevention of pleural thickening mainly involves avoiding or reducing the exposure to the risk factors that can cause the condition.

Here are some tips that may help to limit the risk of developing pleural thickening:

• Assess if there are any sources of asbestos exposure in your home or work environment and get them removed.
• Wear a face mask and practice prevention measures to lower the spread of respiratory illnesses such as COVID-19.
• It is advisable to quit smoking or reduce the intake of tobacco and to avoid secondhand smoke as much as possible.
• Avoid anything that irritates the lungs or that causes you to cough.
• Install an air purification system in your home, preferably with the ability to dehumidify the air if living in a moist or humid location.
• Lead a physically active lifestyle and actively build your cardiorespiratory fitness.
• Consume a healthy diet that ranks low on the glycemic index, is hypoallergenic and does not trigger digestive problems.

If experiencing any respiratory symptoms, breathlessness, or sinus issues, it is important to have them checked out by a medical professional as soon as possible. Swift treatment of any respiratory condition can help lower the risk of acquiring pleural thickening and more severe respiratory ailments.

Conclusion

Pleural thickening is a lung disease that affects the pleura, the thin membrane lining the chest cavity and covering the lungs. It is characterized by chest pain and breathlessness, and can increase the risk for mesothelioma, an aggressive cancer of the pleura. There are several causes for pleural thickening, with the most common ones being asbestos exposure, respiratory infections, lung diseases, and chest injuries. Pleural thickening can usually be managed with medication and drainage. Surgery is often not required, although it may be indicated in the case of fibrosis or malignancy. With further research and development, pleural scarring may be treatable in the future with injectable agents that dissolve fibroids or with modified stem cells.

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