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The word “pulmonary” means lung and the word “fibrosis” means scar tissue— similar to scars that you may have on your skin from an old injury or surgery. So, in its simplest sense, pulmonary fibrosis (PF) means scarring in the lungs. Over time, the scar tissue can destroy the normal lung and make it hard for oxygen to get into your blood. Low oxygen levels (and the stiff scar tissue itself) can cause you to feel short of breath, particularly when walking and exercising. Pulmonary fibrosis isn’t just one disease. It is a family of more than 200 different lung diseases that all look very much alike. The PF family of lung diseases falls into an even larger group of diseases called the interstitial lung diseases (also known as ILD), which includes all of the diseases that have inflammation and/or scarring in the lung. Some interstitial lung diseases don’t include scar tissue. When an interstitial lung disease does include scar tissue in the lung, we call it pulmonary fibrosis.
No one is certain how many people are affected by PF. One recent study estimated that idiopathic pulmonary fibrosis (or IPF, which is just one of more than 200 types of PF) affects 1 out of 200 adults over the age of 60 in the United States—that translates to more than 200,000 people living with PF today. Approximately 50,000 new cases are diagnosed each year and as many as 40,000 Americans die from IPF each year.
CAUSES & SYMPTOMS OF PULMONARY FIBROSIS
It can be challenging for doctors to figure out what causes PF. Sometimes they are able to identify one or more causes of your disease, which are discussed here. PF of unknown cause is called “idiopathic”
There are five main categories of identifiable causes of pulmonary fibrosis: Drug-induced, Radiation-induced, Environmental, Autoimmune, and Occupational. In the United States, Environmental and Autoimmune causes seem to be the most common types of PF of known cause.
This table shows some of the clues that doctors use to identify these known causes of PF.
TYPE OF PULMONARY FIBROSIS |
CLUES THAT DOCTORS USE |
Drug-induced |
Prior or current use of amiodarone, nitrofurantoin, chemotherapy, methotrexate, or other drugs known to affect the lungs |
Radiation-induced |
Prior or current radiation treatment to the chest |
Environmental (called
hypersensitivity pneumonitis) |
Exposure to mold, animals, or other triggers ("squeaks" heard in the lung) |
Autoimmune (called connective tissue disease-related) |
Joint inflammation, skin changes (particularly on the fingers and face), dry eyes or mouth, abnormal blood tests |
Occupational (called pneumoconiosis) |
Prior or current exposure to dusts, fibers, fumes, or vapors that can cause PF (such as asbestos, coal, silica, and others) |
Idiopathic |
When no cause can be identified |
Some MEDICATIONS can cause PF. Drugs used to treat cancer (chemotherapy), drugs used to treat abnormal heart rhythms (such as amiodarone), drugs used to treat inflammatory conditions (such as methotrexate), and an antibiotic used to treat urinary tract infections (nitrofurantoin) are some of the better known drugs that can cause injury, inflammation, and scarring in the lungs. Numerous other drugs have been implicated as causes of PF in some cases.
RADIATION to the chest for lymphoma; Hodgkin’s disease; or breast, lung, and other cancers can injure the lung and cause fibrosis.
ENVIRONMENTAL CAUSES OF PF are typically called hypersensitivity pneumonitis (HP) or chronic hypersensitivity pneumonitis. HP occurs when the lungs react with inflammation and scarring after breathing in mold spores, bacteria, animal proteins (especially from indoor or caged birds), or other known triggers. No one is certain why some people are so susceptible to developing HP and others are not.
AUTOIMMUNE DISEASES are also called connective tissue diseases, collagen vascular diseases, or rheumatologic diseases. “Auto” means self and “immune” refers to your immune system. So if you have an autoimmune disease affecting your lungs, it means that your body’s immune system is attacking your lungs. Examples of autoimmune diseases that can cause PF include
- • Rheumatoid arthritis;
- • Scleroderma (also called systemic sclerosis);
- • Sjögren’s syndrome; and
- • Polymyositis, dermatomyositis, and antisynthetase syndrome.
OCCUPATIONAL CAUSES OF PF, also called pneumoconiosis, can develop after significant exposure to a wide variety of inorganic dusts, including asbestos, silica, coal dust, beryllium, and hard metal dusts.
ARE THERE GENETIC OR INHERITED FORMS OF PULMONARY FIBROSIS?
Yes, but in most cases, it is not as straightforward as inheriting blue eyes or red hair. There are three different scenarios:
1) Did the genes I inherited from my parents contribute to PF even if I am the only one in my family with PF?
Yes. The risk of developing most human diseases is influenced by the genes you inherited from your parents. There have been several genes identified that appear to increase the risk of developing PF when an abnormal form of the gene is inherited. There are no official medical guidelines on whether or not genetic testing should be performed if you have PF, although in some cases, your doctor might wish to test you for one or more abnormal forms of these genes.
2) Can PF run in the family?
Yes. Anywhere from three to 20% of people with PF have another family member with PF. But this doesn’t mean that up to 20% of your family members will develop PF. In most cases, the chance that one of your family members will develop PF is very low. We encourage you to talk to your doctor or to a genetic counselor about the chances that one of your family members will develop PF.
3) Are there specific types of PF where the entire disease is due to one gene?
Yes. There are a few rare genetic forms of PF that can affect both children and adults when just a single gene is inherited in an abnormal form (usually from both parents). Hermansky-Pudlak syndrome is an example of a genetic form of PF that simply requires abnormalities in one gene. People living with Hermansky-Pudlak syndrome often also have very light skin pigmentation (due to low levels of melanin in their skin) and bleeding problems (due to poorly functioning platelets in their blood). Dyskeratosis congenita is another example of a genetic form of PF that can be accompanied by poorly growing fingernails, changes in skin pigmentation, increased risks of developing problems in the bone marrow, and other conditions.
WHAT IS IDIOPATHIC PULMONARY FIBROSIS?
Idiopathic Pulmonary Fibrosis (IPF) is a scarring disease of the lungs of unknown cause. To make a diagnosis of IPF, your doctor will perform a thorough history to try to identify potential exposures or other diseases that might lead to scarring of the lung.
If diagnosed, over time scarring can worsen making it hard to take a deep breath. The lungs then cannot take in enough oxygen to oxygenate the blood. IPF is a form of interstitial lung disease, primarily involving the interstitium or the tissue and space around the air sacs of the lungs, and not directly affecting the airways or blood vessels.
There are various kinds of interstitial lung disease that can also be caused by inflammation and/or fibrosis. These types of IPF are treated a bit differently. It is important to work with your health care provider to determine if you have IPF or another form of interstitial lung disease.
If a plausible cause is found, then you do not have IPF. The scarring pattern of IPF is technically called usual interstitial pneumonia (UIP). Your doctor will use detailed X-rays of your lungs called high-resolution computed tomography (HRCT) and sometimes a lung biopsy to look for this pattern. A diagnosis of IPF requires that your doctor cannot find a cause and the presence of a pattern of UIP on either HRCT or a surgical lung biopsy sample.
Although IPF is still considered to be a disease of unknown cause, we do know some factors that increase the risk of getting IPF, including aging (IPF is rare before age 50), cigarette smoking, and having certain genetic predispositions.
SIGNS & SYMPTOMS OF IDIOPATHIC PULMONARY FIBROSIS
The most common symptoms of IPF are dry, hacking cough and shortness of breath. Symptoms may be mild or even absent early in the disease process. As the lungs develop more scar tissue, symptoms worsen. Shortness of breath initially occurs with exercise, but as the disease progresses patients may become breathless while taking part in everyday activities, such as showering, getting dressed, speaking on the phone, or even eating.
Due to a lack of oxygen in the blood, some people with idiopathic pulmonary fibrosis may also have “clubbing” of the fingertips. Clubbing is a thickening of the flesh under the fingernails, causing the nails to curve downward. It is not specific to IPF and occurs in other diseases of the lungs, heart, and liver, and can also be present at birth.
Other common symptoms of pulmonary fibrosis include:
- • Fatigue and weakness
- • Discomfort in the chest
- • Loss of appetite
- • Unexplained weight loss
PULMONARY FIBROSIS DIAGNOSIS
How do doctors recognize and diagnose pulmonary fibrosis? There are three consequences of PF. Doctors use these consequences to recognize that someone has PF.
- STIFF LUNGS— Scar tissue and inflammation make your lungs stiff. Stiff lungs are hard to stretch, so your breathing muscles have to work extra hard just to pull air in with each breath. Your brain senses this extra work, and it lets you know there’s a problem by triggering a feeling of breathlessness(or “shortness” of breath) while exerting yourself. Also, stiff lungs hold less air (they shrink up a bit). Doctors take advantage of this “shrinking” to diagnose and track the disease using breathing tests (called Pulmonary Function Tests) that measure how much air your lungs can hold. The more scar tissue your lungs have, the less air they will hold.
- LOW OXYGEN LEVELS IN THE BLOOD— Scar tissue blocks the movement of oxygen from the inside of your air sacs into your bloodstream. For many people living with pulmonary fibrosis, oxygen levels are only reduced a little bit while resting, but their oxygen levels drop quite a bit during exertion. The brain can sense these low oxygen levels, triggering breathlessness. Doctors will check your oxygen levels to see if they drop after walking, a clue that PF might be present. Doctors also often prescribe oxygen to be used through a nasal cannula or a facemask during exertion and sleep for those with PF. As pulmonary fibrosis progresses, oxygen may be needed 24 hours a day.
- “CRACKLES”— Your doctor may have told you that “crackles” were heard in your lungs. Crackles (also called “rales”) sound like Velcro being pulled apart. They are heard in many lung diseases because any type of problem affecting the air sacs (such as PF, pneumonia, or a buildup of fluid in the lungs from heart failure) can cause crackles. Some people with pulmonary fibrosis don’t have crackles, but most do.
Once your doctor recognizes that you might have pulmonary fibrosis, the next step is to try to diagnose the specific kind of PF you have— there are more than 200 different kinds. Doctors typically start by asking many questions, performing a careful physical examination, and ordering a lot of blood tests. See Causes for more information.
A doctor will also use a special kind of X-ray of the chest, called a high-resolution computed tomography (HRCT) scan, so that they can see what your lung tissue looks like. HRCT scans give a close-up view of the lungs, providing more detail than routine CT scans (also known as CAT scans). Healthy lung tissue looks nearly black on a CT scan. Scar tissue and inflammation both appear grey or white. Many forms of PF look similar on a CT scan to the untrained eye, but subtle findings on HRCT scans are critically important when trying to identify which type of PF you have.
Sometimes, even after all of the testing is complete, a doctor will still not have an answer and will have to perform a lung biopsy to sort out which of the 200 different types of pulmonary fibrosis you have. When indicated, a lung biopsy can also help you and your doctor decide which treatments might be helpful.