The lungs are surrounded by a moist, double-layered membrane called the pleura. This lining allows comfortable movement between the lungs and the ribcage as a person breathes. Inflammation of the membrane is called pleurisy.
When the pleura is inflamed, it becomes rough and stiff, causing the two layers to rub against each other. The rubbing produces a sound called a "friction rub," which can be heard with a stethoscope. Pleurisy causes extreme pain with each breath, sneeze and cough.
Viral infections are the most common cause of pleurisy; however, it can also be caused by pneumonia, tuberculosis, cancer, chest injury, and other lung disorders. Treating pleurisy requires treating the underlying illness.