Fibrosis refers to scar tissue that has replaced healthy tissue. This is what happens in the lungs of people with pulmonary fibrosis. Inflammation (swelling) in the lungs usually happens before or at the same time as the formation of scar tissues.
There are several substances known to cause lung fibrosis, but people often develop lung fibrosis even when there is no apparent cause. When the cause is unknown, it's called idiopathic.
Idiopathic pulmonary fibrosis is a serious condition whose cause is not well understood. Another condition very similar to idiopathic pulmonary fibrosis can happen in some people with certain diseases, especially autoimmune diseases like systemic lupus erythematosis or scleroderma. Whether this other condition is the same thing as idiopathic pulmonary fibrosis or slightly different is unknown.
When pulmonary fibrosis is idiopathic, it most often occurs in people 50 years of age and older, but people of any age can develop it. Pulmonary fibrosis can be detected at an early stage or late stage but usually gets worse with time. Sometimes it progresses slowly but it can also progress quickly over just a few years or even months.
There are many potential causes of pulmonary fibrosis, such as:
- rheumatoid arthritis
- mineral dusts - coal, silicon, asbestos (asbestosis), metals
- poisonous industrial gases such as chlorine and sulphur dioxide
- radiation treatment to the chest
- poisons - particularly paraquat
- medications (e.g., nitrofurantoin, amiodarone, bleomycin, cyclophosphamide methotrexate)
The cause of pulmonary fibrosis, especially when it is idiopathic, is poorly understood. It probably involves deregulation of the immune system in the lungs, but some experts still think it might be caused by an unknown environmental exposure, or even an unusual infection.
A few families are particularly affected by idiopathic pulmonary fibrosis, which may be categorized into two forms - an environmental form and a rarer genetic form. Pulmonary fibrosis is more likely caused by environmental factors in genetically susceptible people. These people have immune systems that overreact in the presence of particular irritants or organisms. This would be typical of autoimmune disease.
The mechanism of the disease is as follows: The lungs become inflamed, usually for no clear reason. White blood cells and liquid fill the alveoli (the lung's tiny air pockets where oxygen is transferred to the blood). If the liquid remains for long enough, blood-clotting agents solidify, leaving scars that can interfere with the function of the alveoli.
The blood vessels of the lungs are separated from the air pockets by walls called interstitia. The interstitium allows oxygen to reach the blood, and carbon dioxide from the blood to pass into the lungs to be breathed out. Fibrosis damages this membrane, thickening it and thus reducing the lungs' ability to add oxygen and remove carbon dioxide from the blood.
Symptoms and Complications
For the majority of people, the symptoms of pulmonary fibrosis come on slowly over the course of months to years, but for some people the symptoms can develop more rapidly.
Most people with pulmonary fibrosis first see their doctor about increasing shortness of breath during exercise. Some also have a cough. These are often the only symptoms of early pulmonary fibrosis, but you might also feel one or more of the following symptoms:
- loss of stamina
- loss of appetite
- weight loss
- diffuse chest pain
Later on, symptoms can include:
- shortness of breath without exercise - eating, talking, or just resting
- cyanosis (blue lips, nail beds, and sometimes skin due to lack of oxygen in the tissue)
- clubbing of the fingers (enlarged fingertips)
Pulmonary fibrosis can lead to several severe complications. Because the lungs don't take in oxygen as well, low blood oxygen levels (hypoxemia) can develop. Lack of oxygen can affect the entire body.
Another complication of pulmonary fibrosis is pulmonary hypertension (high blood pressure in the arteries of the lungs). Scar tissue in the lungs can make it more difficult for blood to flow through them. The increased pressure makes the heart work harder and leads to a weakened and enlarged heart, reducing its pumping efficiency and producing heart failure. This is suspected when people develop fluid accumulations in the abdomen, leg swelling, or prominent pulsations in neck veins.
Making the Diagnosis
Lung diseases all tend to have much the same symptoms, so a thorough history, examination, pulmonary function tests, and chest X-ray, while all essential, may not be enough to identify pulmonary fibrosis, especially if it's due to no known cause (idiopathic).
Your doctor may also order blood tests and heart tests to check for underlying causes of your symptoms. A computed tomography (CT) scan may also be done to check for changes within the lungs. An exercise test may also be suggested to see how well your lungs work during exertion.
The definitive diagnostic test is a lung biopsy - obtaining a sample of lung tissue for examination in a laboratory.
The best way to do this is in the operating room, where a piece of lung tissue is surgically removed. You can expect to be hospitalized for several days after this kind of procedure. Sometimes, people who might benefit from this kind of biopsy are too sick to go through with it.
A quicker but less accurate way of doing a lung biopsy can be done non-operatively through bronchoscopy, which is a test that involves passing a narrow tube with a light and camera on the end through the nose or mouth and into the lungs. Once the device is in place, a tool called a forceps can be passed through it to take a small sample biopsy of the lung. People can usually go home on the same day that the procedure is done.
Treatment and Prevention
Once scar tissue has formed, it can't be reversed or removed, so treatment is aimed at slowing the progression of the disease and improving symptoms.
Unfortunately, the treatments we have are limited. For many people with pulmonary fibrosis, the only treatments are for symptomatic relief, such as oxygen therapy. Relatively young and healthy people with pulmonary fibrosis may be candidates for a lung transplant.
In pulmonary fibrosis caused by some other disease such as rheumatoid arthritis, treating the underlying disease is the best approach and usually reduces lung inflammation.
In idiopathic pulmonary fibrosis, medications that suppress the immune system may prevent new scarring, but most of these medications have not been found to be very effective. The corticosteroid prednisone* is the treatment most often given. Other immune suppressants like cyclophosphamide are also sometimes tried. Pulmonary rehabilitation is a standard part of treatment for people with pulmonary fibrosis. This can involve an exercise program, breathing exercises, and stress management.
Exercise can improve the body's ability to provide oxygen to the tissues, and maximize the efficiency of healthy lung tissue. People with advanced pulmonary fibrosis may need oxygen equipment in order to maintain an adequate supply of oxygen in their circulation.
People with pulmonary fibrosis should quit smoking.
It's difficult to prevent a disease when you don't know what causes it, so there's no generally accepted preventive advice for pulmonary fibrosis. However, people who have jobs that increase their risk of developing pulmonary fibrosis (e.g., farmers who work with hay, miners, welders, sandblasters, demolition workers) should do what they can to minimize exposure (e.g., wearing masks).
*All medications have both common (generic) and brand names. The brand name is what a specific manufacturer calls the product (e.g., Tylenol®). The common name is the medical name for the medication (e.g., acetaminophen). A medication may have many brand names, but only one common name. This article lists medications by their common names. For information on a given medication, check our Drug Information database. For more information on brand names, speak with your doctor or pharmacist.
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