Inflammation of the pleura, the two-layered membrane separating the lungs from the chest wall
Normally, when people breathe, the two layers of the pleura (the membrane that separates the lungs from the chest wall) slide over each other, allowing the lungs to inflate and deflate smoothly. In pleurisy, inflammation of the pleura prevents the layers from moving over each other easily, and they grate as they rub against each other, causing sharp, severe chest pain when inhaling.
Pleurisy may be caused by a viral illness, such as influenza, which affects the pleura itself. However, the disorder is often a reaction to damage to the lung just beneath the pleura. This lung damage may be due to pneumonia or pulmonary embolism, in which the blood supply to part of the lung is blocked by a blood clot. The pleura can also be affected by primary lung cancer. Occasionally, an autoimmune disorder, such as rheumatoid arthritis or systemic lupus erythematosus, in which the immune system attacks healthy tissues, affects the pleura and leads to pleurisy.
If an infection or a pulmonary embolism is the cause of the inflammation, the symptoms usually develop rapidly over 24 hours. In other cases, the symptoms occur gradually. They may include:
Sharp chest pain that causes you to catch your breath on inhaling.
Difficulty in breathing.
The pain is often restricted to the side of the chest affected by the underlying inflamed pleura. In some cases, fluid accumulates between the layers of the pleura (see Pleural effusion). This condition may actually lessen the pain because it eases the movements of the pleural layers over each other.
If you suspect that you have pleurisy, you should consult your doctor within 24 hours. He or she may be able to hear the layers of the pleura rubbing against each other when listening to your chest with a stethoscope. You may need a chest X-ray to check for a problem in the underlying lung or for the presence of a pleural effusion.
You may be prescribed nonsteroidal anti-inflammatory drugs to relieve the pain and inflammation. You may also find that holding the affected side while coughing helps to relieve the discomfort. In addition, you will probably need treatment for the underlying condition that is causing the pleurisy. For example, if a lung infection is the cause, you may be prescribed a course of antibiotics. If you have a pulmonary embolism, you will probably be given anticoagulant drugs (see Drugs that prevent blood clotting). In the majority of affected people, the condition clears up within 7–10 days of starting treatment.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.