Pleurisy, also known as pleuritis, is the inflammation of the pleura, which is the thin double-layer membrane which surrounds the lungs. It is usually caused by either an infection of the lung or injury. Pleurisy is characterized by the build-up of fluids between the two layers that make up the pleura or between the pleura and the lung. This condition causes pain when breathing, and coughing. Treatment: drainage of fluids, and antibiotics to treat the infectious disease that has originated pleurisy.