Idiopathic pulmonary fibrosis is a serious disease where the tiny air sacs of the lungs (the alveoli) and the lung tissue next to the alveoli become damaged and scarred. The main symptom is shortness of breath that gradually gets worse. The exact cause is not known. Idiopathic pulmonary fibrosis used to be called cryptogenic fibrosing alveolitis. The exact cause is not known (hence the term idiopathic). It was thought that inflammation within the alveoli played a big role in the development of IPF and that this inflammation led to scarring (fibrosis). This led to the name cryptogenic fibrosing alveolitis. However, treatments that help to reduce inflammation are not always effective. Therefore, the role of inflammation has recently been brought into question.

The current thinking is that somehow the cells that line the alveoli are damaged in some way. The cells then try to heal themselves. But, this healing process becomes out of control, causing thickening and damage to the walls of the alveoli, and scarring of the alveoli and lung tissue. The thickening and scarring reduces the amount of oxygen that can pass into the blood vessels from affected alveoli. Therefore, as the disease progresses, less oxygen than normal is passed into the body when you breathe. Various things have been suggested as potential causes, or triggers, of the initial damage to the cells lining the alveoli. These include:

• Cigarette smoking. The disease is more common in people who smoke or have been smokers at some time.
• Viral infections. These include viruses such as the Epstein-Barr virus that causes glandular fever, and the hepatitis C virus.
• Certain medicines.
• Pollutants in the environment.
• Gastro-oesophageal reflux disease. In this condition there is long-standing reflux of stomach contents into your gullet (oesophagus), which you may then inadvertently inhale into your lungs. See separate leaflet called Acid Reflux and Oesophagitis for more details.
• IPF also seems to run in some families. However, in about 4 out of 5 cases, there is no family history of the disease.

A similar fibrotic lung condition sometimes occurs as a result of exposure at work to certain metals, wood dusts and other chemicals, and as a side-effect to certain medicines. These conditions are not idiopathic, as the cause can be identified. If you have suspected lung fibrosis, your doctor is likely to ask you about your work history to rule out these conditions.

It is rare. About 2 in 10,000 people develop this disease. However, it seems to be becoming more common. It can affect anybody at any age but it most commonly in older age groups. It seems to be more common in men than in women.

Symptoms tend to develop gradually:

• Shortness of breath that gradually becomes worse is the main symptom. This is due to the reduced amount of oxygen that gets into the bloodstream. Shortness of breath on exertion may be noticed at first. This may be passed off as 'just getting older' for a while until the shortness of breath gets worse.
• A dry cough often develops (a cough with little or no sputum).
• Finger or toenail clubbing occurs in about half of cases. Clubbing is a painless swelling at the base of the nails. The cause of clubbing is not clear. It occurs in people with various chest and heart diseases.
• Tiredness.
• An increased risk of developing chest infections.

As the condition progresses, symptoms can sometimes quickly become worse (called an acute exacerbation). Periods of worse symptoms may be followed by periods where there seems to be some improvement. If the condition becomes severe then heart failure may develop. This is due to the reduced level of oxygen in the blood and changes in the lung tissue, which can cause an increase in pressure in the blood vessels in the lungs. This increase in pressure can put a strain on the heart muscle, leading to heart failure. Heart failure can cause various symptoms, including worsening breathlessness and fluid retention. The above symptoms, combined with crackles heard by a doctor listening to your lungs with a stethoscope, can suggest the diagnosis. A chest X-ray may show a typical scarring pattern in the lungs, suggestive of the disease. Special breathing tests can also show changes that raise suspicion. Your doctor may advise that they refer you to a chest specialist if they suspect that you have IPF.

To confirm the diagnosis and to assess the severity of the disease, a CT scan of the lung and/or a lung biopsy are usually needed. A special type of CT scanning, called high-resolution CT (HRCT) scanning, is commonly used. A lung biopsy is a procedure where a small sample of lung tissue is taken by a small operation. A keyhole procedure is normally used. The sample is looked at under a microscope. IPF causes a typical appearance of the tiny air sacs of the lungs (the alveoli) and nearby lung tissue. This can be seen when the biopsy sample is examined. Sometimes the specialist may suggest that they take samples of your lung cells in another way to examine them. This is usually done through a procedure known as a bronchoscopy. A small, flexible telescope is passed down your breathing tubes so that the samples can be collected. An ultrasound examination of your heart (echocardiogram) may be done if it is suspected that you have developed heart failure.

At present there is no cure for IPF and the optimal treatment has not yet been found. The aim of treatment is to suppress the symptoms as much as possible. Because IPF was originally thought to be due to inflammation of the tiny air sacs of the lungs (the alveoli) leading to scarring, treatment has been based on medicines to help reduce this inflammation. These included treatments with steroids and other newer medicines (see below). One or more of the following options may be advised to help to improve symptoms and to slow down the progression of the disease:

Steroid medication may be tried, usually in combination with immunosuppressant medicines. Previous studies showed that steroid medication improved symptoms in about 1 in 4 affected people. However, some doctors now wonder if the people for whom the steroids worked actually had another type of lung disease. If steroids are prescribed, a high dose is used at first and then reduced to a lower maintenance dose. If there is no improvement after a few months then the steroids are stopped. Some people who take steroids develop side-effects. See separate leaflet called Oral Steroids for more details of possible side-effects. No treatment is another option. Medication can cause side-effects in some people. The risk of side-effects has to be balanced with the chance of improving symptoms and slowing down the progression of the disease. No treatment may be advised, particularly for elderly people if their symptoms are mild or are not getting much worse. A chest specialist usually keeps the situation under review. Oxygen treatment used in the home may be required if symptoms become severe. Pulmonary rehabilitation courses may help some people. The courses include education about IPF and physical exercise, as well as psychological and social support. Ask the chest clinic that you attend about your nearest course. Stop smoking if you are a smoker, Get immunised against influenza and pneumococcus. They protect against infections that can be particularly severe if you have a disease of the lung. A lung transplant may be an option. This is becoming more common, particularly in younger people who develop severe disease despite medication. Various newer treatments have been shown to be effective treatments for IPF. They do not cure the illness but they can improve symptoms and slow the progression of the illness. These medicines include pirfenidone and nintedanib.

The progression of the disease can vary greatly. Some people respond to medication which may slow the progression of the disease but, in others, it makes little difference. Some people remain stable for many years after being diagnosed but others deteriorate much more rapidly. It is difficult to predict at the outset how fast the disease will progress for each affected individual. Lung transplantation has been shown to improve survival in those people for whom it is suitable and so is being increasingly used as a treatment. Newer treatments with medicines may also be shown to be of benefit in the future.