Lung Disease & Respiratory Health Center

Understanding Pleurisy -- the Basics

What Is Pleurisy?

Pleurisy, also called pleuritis, is an inflammation of the pleura, which is the moist, double-layered membrane that surrounds the lungs and lines the rib cage. The condition can make breathing extremely painful. Sometimes it is associated with another condition called pleural effusion, where excess fluid fills the area between the membrane's layers.

The double-layered pleura protects and lubricates the surface of the lungs as they inflate and deflate within the rib cage. Normally, a thin, fluid-filled gap -- the pleural space -- allows the two layers of the pleural membrane to slide gently past each other. But when these layers become inflamed, with every breath, sneeze, or cough their roughened surfaces rub painfully together like two pieces of sandpaper.

In some cases of pleurisy, excess fluid seeps into the pleural space, resulting in pleural effusion. This fluid buildup usually has a lubricating effect, relieving the pain associated with pleurisy as it reduces friction between the membrane's layers. But at the same time, the added fluid puts pressure on the lungs, reducing their ability to move freely. A large amount of fluid may cause shortness of breath. In some cases of pleural effusion, this excess liquid can become infected.

What Causes Pleurisy?

Viral infection is probably the most common cause of pleurisy. Other causes include the following:

• Lung infections, such as pneumonia and tuberculosis
• Other diseases such as systemic lupus erythematosus (lupus), rheumatoid arthritis, cancer, liver diseases, and  pulmonary embolism
• Chest injuries
• Drug reactions

Pleurisy and pleural effusion are generally only as serious as the underlying disease causing it. If you have either of these conditions, you may already be undergoing treatment for the underlying disease; if not, seek medical attention immediately.

A pleural effusion can occur without pleurisy. Kidney disease, heart failure, and liver disease can cause pleural effusion without inflammation or pain.