Pulmonary fibrosis : Canadian Lung Association

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Pulmonary fibrosis

Causes | Symptoms | Idiopathic pulmonary fibrosis | Treatment | Outcome

Pulmonary fibrosis is a chronic disease causing swelling and scarring of the alveoli (air sacs) and interstitial tissues of the lungs. Pulmonary fibrosis is the abnormal formation of fibre-like scar tissue in the lungs. The scar formation is preceded by, and associated with, inflammation.

Some common and some rare diseases can cause pulmonary fibrosis, but in the majority of cases the cause is never found (idiopathic pulmonary fibrosis). Pulmonary fibrosis can be a mild or severe disease; it can be so mild as to cause few symptoms, or it can be fatal.

How does pulmonary fibrosis progress?

If the disease progresses, the lung tissues eventually thicken and become stiff. The work of breathing then becomes difficult, causing breathlessness. It can run a gradual course, remain unchanged or run a rapid course. It can also be fatal.

The alveoli (the tiny grape-like air sacs that take oxygen into the lungs and release carbon dioxide), are affected. Fibrosis twists the aveoli out of shape. Lung capillaries (small blood vessels) also can be distorted by pulmonary fibrosis. In addition, the tissues between and surrounding the alveoli are changed by fibrosis, thus completely disordering the basic architecture of the inner lung. These "in-between" spaces are called the "interstitium".

This condition has a number of causes and is known by many different names. "Interstitial pulmonary fibrosis" is perhaps the most common name, but other terms frequently used include: "fibrosing alveolitis", "intersititial pneumonitis" and "Hamman-Rich syndrome".

What causes pulmonary fibrosis?

Pulmonary fibrosis is a complicated illness that can originate from many different causes. There are over 140 known causes or associations with pulmonary fibrosis. It appears that the lung is reacting to some insult by developing inflammation and fibrosis (scarring). The nature of the initial insult is not always known and although doctors may say that pulmonary fibrosis is due to a given disease (for example, sarcoidosis) they may not often know the specific causes of those diseases either.

The most frequent causes of pulmonary fibrosis are sarcoidosis — fibrosis associated with certain occupational diseases — and pulmonary fibrosis in which the causes are not known ("idiopathic").

Occupational diseases and pulmonary fibrosis

Many jobs, particularly those that involve working with asbestos, ground stone or metal dust, can cause pulmonary fibrosis. The small particles are inhaled, damage the alveoli and cause fibrosis. Some organic substances, such as mouldy hay can also cause pulmonary fibrosis; this is known as farmer's lung.

Asbestosis and pulmonary fibrosis

Asbestosis is usually caused when small needle-like particles of asbestos are inhaled into the lungs. This can cause lung scarring (pulmonary fibrosis) and in addition can lead to lung cancer.

Cigarette smoking has an interactive relationship with asbestos — the asbestos worker who smokes has a much higher chance of developing lung cancer than does the non-smoker.

Silicosis and pulmonary fibrosis

Silicosis is another disease producing pulmonary fibrosis in which the cause is known. It is a disease that results from breathing in free crystalline silica dust.

All types of mining in which the ore is extracted from quartz rock can produce silicosis if precautions are not taken. This includes the mining of gold, lead, zinc, copper, iron, anthracite (hard) coal and some bituminous (soft) coal. Workers in foundries, sandstone grinding, tunneling, sandblasting, concrete breaking, granite carving and china manufacturing also encounter silica.

Large silica particles are stopped in the upper airways. But the tiniest specks of silica can be carried down to the alveoli where they lead to pulmonary fibrosis.

Silicosis can be either mild or severe, in direct proportion to the percentage and concentration of silica in the air and the duration of exposure.

Silicosis can be prevented by measures specifically designed for each industry and each job. Dust control is essential. Sometimes this is accomplished by the wetting down of mines, improved ventilation or the wearing of masks.

Idiopathic pulmonary fibrosis

Although a number of separate diseases can initiate pulmonary fibrosis, many times the cause is unknown. When this happens, the condition is called "idiopathic (of unknown origin) pulmonary fibrosis".

In idiopathic pulmonary fibrosis, careful examination of the patient's environmental and occupational history gives no clues to the cause.

Some doctors and scientists believe that the disease is an infectious or allergic condition, however bacteria and other micro-organisms are not routinely found in the lungs of patients with idiopathic pulmonary fibrosis. On the other hand, the condition does sometimes appear to follow a viral-like illness.

Other diseases that can cause pulmonary fibrosis:

tuberculosis
rheumatoid arthritis
systemic Lupus Erythematosis
systemic Sclerosis
grain handler's lung
mushroom worker's lung
bagassosis
detergent worker's lung
maple bark stripper's lung
malt worker's lung
paprika splitter's lung
bird breeder's lung
Hermansky Pudlak yndrome

Some medicines that can cause pulmonary fibrosis

Certain strong medicines may have the undesirable side effect of causing pulmonary fibrosis. Some of them are:

nitiofurantoin (sometimes used for urinary tract infections)
amiodarone (sometimes prescribed for an irregular heart rate)
bleomycin, cyclophosphamide and methotrexate (sometimes prescribed to fight cancer)

Who is at risk for pulmonary fibrosis?

Patients of any age with any of the diseases listed above, or with exposure to any of the drugs listed above, may develop pulmonary fibrosis, but this is rare. Patients who develop idiopathic pulmonary fibrosis are usually middle-aged men and women, and there appears to be no sexual, racial or geographical tendency.

What are the symptoms of pulmonary fibrosis?

Breathlessness is the hallmark of pulmonary fibrosis. Many lung diseases show breathlessness as the main symptom — a fact that can complicate and confuse diagnosis. Usually the breathlessness of idiopathic pulmonary fibrosis first appears during exercise. The condition may progress to the point where any exertion (serious physical activity) is impossible.

A dry cough is a common symptom. The fingertips may enlarge at the ends and take on a bulbous appearance. This is often referred to as "clubbing".

How is pulmonary fibrosis diagnosed?

A chest X-ray may give some clues. Pulmonary function tests, which reveal the efficiency of a patient's breathing mechanism, may give other indications.

Bronchoalveolar lavage (a test which permits removal and examination of cells in the lower respiratory tract) is sometimes used for diagnosis. Another diagnostic technique involves injection with gallium 67, a substance which is absorbed by inflamed areas that can be seen later on sensitized film.

At some point, a lung biopsy may be performed so that cells in and around the alveoli can be examined.

What is the treatment for pulmonary fibrosis?

If one of the known causes of pulmonary fibrosis exists, then treatment of that underlying disease or removal of the patient from the environment causing the disease can be effective.

Many times treatment is limited only to treating the inflammatory response that occurs in the lungs. This is done in the hope that stopping the inflammation will prevent the laying down of scar tissue or fibrosis in the lungs and thus stop the progression of the disease. Corticosteroids are the drugs which are usually administered in an attempt to stop the inflammation. The advantage of this treatment has not been proven in every case, although it does appear that if the drugs are given early on in the course of the disease, there is a better chance of improvement. Corticosteroid medications can have various side effects and so patients taking these medications must be frequently reassessed by their doctors in order to judge the safety and benefit of this therapy.

Other drugs have been tried but there is not a lot of convincing evidence of their effectiveness.

Although drug therapy of pulmonary fibrosis may not always be successful, there is much that can be done in the way of supportive therapy that will ease the breathlessness that accompanies this condition. Rehabilitation and education programs can help considerably in teaching patients how to breathe more efficiently (using as little energy as possible) and to perform their activities of daily living with less breathlessness. Sometimes supplemental oxygen therapy is required in order to treat breathlessness. Early treatment of chest infections is required. Smoking must be discontinued, as the effects of tobacco will aggravate the shortness of breath.

What is the outcome of pulmonary fibrosis?

Many times the disease is mild with few symptoms and does not progress significantly with the years. In other cases, when pulmonary fibrosis is due to some other underlying disease, such as rheumatoid arthritis, progression of the lung condition may reflect progression of the underlying diseases. Very rarely pulmonary fibrosis has a sudden onset and rapidly progresses to death from respiratory failure over a period of weeks. However, the usual course of pulmonary fibrosis, particularly idiopathic pulmonary fibrosis, is one of slowly progressive scarring of the lungs. The duration and speed of this process is variable. Some patients do not respond to therapy and have a slow deterioration over months to years, eventually ending in death when lungs can no longer function adequately. In other cases, patients respond to therapy.