Pulmonary fibrosis (idiopathic) - Causes of idiopathic pulmonary fibrosis

The exact cause of idiopathic pulmonary fibrosis (IPF) is not known. Idiopathic means having no known cause.

The current theory is that IPF is triggered when cells that line the lung alveoli (air sacs) become damaged by exposure to one of several substances or viruses.

The damaged cells try to repair themselves but the process becomes uncontrolled, resulting in thickening and scarring (fibrosis) of the alveoli and surrounding lung tissue. The amount of oxygen that can pass from the lungs into the blood is then significantly reduced.

Triggers

A number of factors have been suggested as possible triggers for the initial damage to the cells lining the alveoli. Most experts agree that the two most significant risk factors are:

• being a smoker or having smoked in the past
• occupational exposure to certain types of dust – jobs that involve working with wood, metal, textile, stone, cattle or farming may increase the risk of IPF 

Other possible risk factors include:

• viral infections – such as the Epstein-Barr virus or hepatitis C
• gastro-oesophageal reflux disease (GORD) (where the acid from your stomach rises back up into your throat) – this may be accidentally inhaled into the lungs, causing damage to the alveoli
• chronic aspiration – where food, drink or saliva enter the lungs and is not coughed back up, often due to a related condition
• environmental pollutants or dust
• genetic tendency – the condition appears to run in some families but this only seems to be the case in around 5% of people with IPF

As IPF is such a rare condition it is hard to estimate how much of an impact these risk factors can have on your chance of developing it.