Pleurisy (PLUR-ih-se) is a condition in which the pleura is inflamed. The pleura is a membrane that consists of two large, thin layers of tissue. One layer wraps around the outside of your lungs. The other layer lines the inside of your chest cavity.
                
Between the layers of tissue is a very thin space called the pleural space. Normally this space is filled with a small amount of fluidabout 4 teaspoons full. The fluid helps the two layers of the pleura glide smoothly past each other as you breathe in and out.
                
Pleurisy occurs if the two layers of the pleura become irritated and inflamed. Instead of gliding smoothly past each other, they rub together every time you breathe in. The rubbing can cause sharp pain.
                
Many conditions can cause pleurisy, including viral infections.
                
Other Pleural Disorders
                
Pneumothorax
                
Air or gas can build up in the pleural space. When this happens, it's called a pneumothorax (noo-mo-THOR-aks). A lung disease or acute lung injury can cause a pneumothorax.
                
Some lung procedures also can cause a pneumothorax. Examples include lung surgery, drainage of fluid with a needle,bronchoscopy (bron-KOS-ko-pee), andmechanical ventilation.
                
Sometimes the cause of a pneumothorax isn't known.
                
The most common symptoms of a pneumothorax are sudden pain in one side of the lung and shortness of breath. The air or gas in the pleural space also can put pressure on the lung and cause it to collapse.
                
Pleurisy and Pneumothorax
                

                
A small pneumothorax may go away without treatment. A large pneumothorax may require a procedure to remove air or gas from the pleural space.
                
A very large pneumothorax can interfere with blood flow through your chest and cause your blood pressure to drop. This is called a tension pneumothorax.
                
Pleural Effusion
                
In some cases of pleurisy, excess fluid builds up in the pleural space. This is called a pleural effusion. A lot of extra fluid can push the pleura against your lung until the lung, or part of it, collapses. This can make it hard for you to breathe.
                
Sometimes the extra fluid gets infected and turns into an abscess. When this happens, it's called an empyema (em-pi-E-ma).
                
You can develop a pleural effusion even if you don't have pleurisy. For example,pneumonia, (nu-MO-ne-ah),heart failure, cancer, or pulmonary embolism (PULL-mun-ary EM-bo-lizm) can lead to a pleural effusion.
                
Hemothorax
                
Blood also can build up in the pleural space. This condition is called a hemothorax (he-mo-THOR-aks). An injury to your chest, chest or heart surgery, or lung or pleural cancer can cause a hemothorax.
                
A hemothorax can put pressure on the lung and cause it to collapse. A hemothorax also can cause shock. In shock, not enough blood and oxygen reach your body's vital organs.
                
Outlook
                
Pleurisy and other pleural disorders can be serious, depending on their causes. If the condition that caused the pleurisy or other pleural disorder isn't too serious and is diagnosed and treated early, you usually can expect a full recovery.