Pleurisy. Coloured X-ray of the lungs of a patient with pleurisy, inflammation of the membranes (pleura) that line the chest cavity and lungs. A large area of inflammation (white) is seen obstructing the lung at bottom right. Inflammation of the pleura leads to the lungs rubbing against the chest wall, which causes sharp pain on breathing. Fluid may accumulate in the space between the membranes, causing breathing difficulties. Treatment is of the underlying cause, which in this case is a Staphylococcus infection, but may be a viral infection, cancer or an embolism.