Pleurisy, or pleuritis, is a condition characterized by inflammation of the membrane surrounding the lungs and rib cage. This membrane, known as the pleura, functions to protect and lubricate the lungs during inhalation and exhalation. When the pleura becomes inflamed, it causes sharp chest pains that make breathing difficult.
The pleura is a double layered membrane with a small gap between the layers known as the pleural space. Under normal circumstances, the pleural space is filled with fluid that acts as a lubricant between the lung and rib cage during respiration. When these layers of membrane become inflamed, however, they begin to scrape against each other, causing friction between the layers. This friction results in sharp chest pains when the affected individual breathes, sneezes or coughs.
In some cases, extra fluid begins to collect in the pleural space. This is called pleural effusion. When pleural effusion occurs, it relieves the pain caused by the friction of the membranes rubbing against each other, but in turn creates pressure in the lungs, making it difficult for the patient to fully inhale, often resulting in shortness of breath. Pleurisy can be caused by a variety of things, including viral infections, such as tuberculosis; diseases, such as cancer and lupus; chest injuries; and adverse reactions to certain drugs.