Pleurisy - Causes of pleurisy

Pleurisy is the inflammation of the pleura. It is usually caused by another condition, such as an infection.

In some cases, no cause is indentified.

The pleura

The pleura is the layer located between the lungs and ribcage. It is made up of two parts, one is attached to the ribcage and the other is attached to the lungs.

Between these sections is a thin layer of liquid that lubricates the pleura, helping to reduce friction when you breathe in and out.

If the pleura is inflamed, the surfaces of the two layers can become rough and the fluid can become sticky. This can cause the layers to rub together, resulting in pain and discomfort.

Infection

An infection is the most common cause of pleurisy. Any type of infection has the potential to spread to the pleura, but viral infections are usually responsible.

Viruses known to cause pleurisy include:

• the influenza (flu) virus
• the Epstein-Barr virus - which causes glandular fever
• cytomegalovirus (CMV) - a common virus found in most people which does not usually cause any noticeable symptoms
• parainfluenza - the virus that causes the childhood condition called croup

In some cases, pleurisy is caused by bacteria, such as:

• streptococcal bacteria - often associated with pneumonia, throat infections and some types of skin infections, such as impetigo and cellulitis
• staphylococcal bacteria - often associated with skin infections, food poisoning and, more seriously, blood poisoning (sepsis)

Meticillin-resistant Staphylococcus aureus (MRSA) is a common cause of bacterial pleurisy which can sometimes affect hospital patients. MRSA is a type of bacteria that has developed a resistance to a number of commonly used antibiotics.

Other causes

Other possible causes of pleurisy include:

• injury - if the ribs are bruised or fractured the pleura can become inflamed
• pulmonary embolism - a blood clot that develops inside the lungs
• sickle cell anaemia - a blood disorder that usually affects people of African or Caribbean descent
• chemotherapy and radiotherapy
• HIV or AIDS 
• lung cancer
• mesothelioma - a type of cancer caused by inhaling asbestos

Autoimmune conditions, such as rheumatoid arthritis and lupus, are another possible cause of pleurisy. In these conditions, something goes wrong with the immune system (the body’s natural defence against infection and illness) and it begins to attack healthy tissue.