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Pulmonary Fibrosis

Definition:
As different as financier Laurance Rockefeller and the temperamental actor Marlon Brando may have been, they had one thing in common: Both died of pulmonary fibrosis, a generally fatal illness that scars your lungs and ultimately affects your ability to breathe and obtain enough oxygen.

Pulmonary fibrosis is the end stage of interstitial lung disease, a large group of disorders that cause progressive lung scarring. The current thinking is that pulmonary fibrosis begins with repeated injury to the lining of the alveoli, the small air sacs in your lungs. The damage eventually leads to scarring (fibrosis), which stiffens your lungs and makes breathing difficult.

No cure exists for pulmonary fibrosis, and current treatments often fail to slow the progress of the disease or relieve symptoms. A number of new therapies are in clinical trials, however, and researchers hope that better treatments will become available. In the meantime, a lung transplant may be an option for some people with pulmonary fibrosis.

Causes:
Each time you inhale, air travels to your lungs through two major airways called bronchi. Inside your lungs, the bronchi subdivide like the branches of a tree into a million smaller airways (bronchioles) that finally end in clusters of tiny air sacs (alveoli). You have about 300 million alveoli in each lung. Within the walls of the air sacs are small blood vessels (capillaries) where oxygen is added to your blood and carbon dioxide — a waste product of metabolism — is removed.

In pulmonary fibrosis, microscopic damage to the alveoli causes irreversible scarring of the paper-thin tissue (interstitium) that lines and separates the air sacs. Normally, the air sacs are highly elastic, expanding and contracting like small balloons with each breath. But scarring makes the interstitial tissue stiff and thick and the air sacs less flexible. Instead of being soft and elastic, the air sacs have the texture of a dry, stiff sponge, making breathing much more difficult.

This buildup of scar tissue isn't normal — ordinarily, your body makes just enough tissue to repair damage. But in pulmonary fibrosis, the repair process goes awry. Why this occurs isn't entirely certain, though a genetic predisposition may play a role.

What damages the lungs?
Hundreds of factors can cause the lung damage that eventually leads to pulmonary fibrosis. Some of the most common include :

  • Occupational and environmental factors. Long-term exposure to a number of toxins and pollutants can severely damage your lungs. Workers who routinely inhale silica dust (silicosis), asbestos fibers (asbestosis) or hard metal dust are especially at risk of severe lung disease. So are people exposed to certain chemical fumes such as sulfuric acid, ammonia and chlorine gases. Even chronic exposure to some organic substances, including grain dust, sugar cane, and bird and animal droppings, can damage your lungs. Cigarette smoke may play a role in an uncommon type of interstitial lung disease that eventually ends in pulmonary fibrosis.
  • Radiation. A small percentage of people who receive radiation therapy for lung or breast cancer show signs of lung damage months or sometimes years after the initial treatment. The severity of the damage depends on how much of the lung is exposed to radiation, the total amount of radiation administered, whether chemotherapy also is used and the presence of underlying lung disease.
  • Drugs. Many drugs can damage your lungs, especially chemotherapy drugs (methotrexate, cyclophosphamide); medications used to treat heart arrhythmias and other cardiovascular problems (amiodarone, propranolol); certain psychiatric medications; and some antibiotics (nitrofurantoin, sulfasalazine).
  • Gastroesophageal reflux disease (GERD). Acid reflux, which occurs when stomach acids back up into your food pipe (esophagus), appears to play a significant role in pulmonary fibrosis. Although people with pulmonary fibrosis frequently have GERD, they may not have typical GERD symptoms, such as heartburn and belching.
  • Other medical conditions. Serious lung infections such as tuberculosis and pneumonia can cause permanent lung damage. So can disorders that affect tissue throughout your body, not just your lungs, such as systemic lupus erythematosus, rheumatoid arthritis, dermatomyositis, polymyositis, Sjogren's syndrome and sarcoidosis. In rare cases, scleroderma is associated with a particularly severe form of pulmonary fibrosis.

Idiopathic pulmonary fibrosis: When the cause isn't known
The list of substances and conditions that can lead to pulmonary fibrosis is long. Even so, in most cases, the cause is never found. Pulmonary fibrosis with no known cause is called idiopathic pulmonary fibrosis.

Researchers have several theories about what might trigger idiopathic pulmonary fibrosis, including viruses and exposure to tobacco smoke. And because one type of idiopathic pulmonary fibrosis runs in families, heredity also is thought to play a role, even in people who don't directly inherit the disease.

Risk Factor :
Factors that make you more susceptible to pulmonary fibrosis include :

  • Age. Although pulmonary fibrosis has been diagnosed in children and infants, the disorder is much more likely to affect middle-aged and older adults.
  • Your sex. In general, men are more likely to have pulmonary fibrosis than women are, in part because they have more contact with occupational toxins.
  • Occupational and environmental toxins. You have an increased risk of developing pulmonary fibrosis if you work in mining, farming or construction or you're exposed to pollutants known to damage your lungs.
  • Radiation and chemotherapy. Having radiation treatments to your chest or using certain chemotherapy drugs makes you more susceptible to pulmonary fibrosis.

Risk factors for idiopathic pulmonary fibrosis
Even though the causes of idiopathic pulmonary fibrosis aren't known, researchers have identified certain factors that seem to increase your risk :

  • Smoking. Far more smokers and former smokers develop idiopathic pulmonary fibrosis than do people who have never smoked. The risk seems to increase with the number of years and cigarettes smoked, and secondhand smoke also poses a risk.
  • Genetic factors. A rare type of idiopathic pulmonary fibrosis runs in families. Researchers haven't yet identified the specific genes involved, but they have discovered genetic changes in proteins in the airways and air sacs of people with other types of idiopathic pulmonary fibrosis.
  • Viruses. Many people report developing symptoms of idiopathic pulmonary fibrosis after a viral illness, especially one caused by a herpesvirus such as Epstein-Barr, the same virus that causes mononucleosis. As a result, researchers are investigating the role viruses might play in lung disease.

When to seek medical advice :
By the time signs and symptoms such as breathlessness and cough appear, irreversible lung damage has often already occurred. Still, it's important to see your doctor at the first sign of breathing problems. A number of conditions, many of them more common than pulmonary fibrosis, can affect your lungs, and getting an early and accurate diagnosis is important for proper treatment.

Symptoms:
The most common pulmonary fibrosis symptoms are shortness of breath (dyspnea), especially during or after physical activity, and a dry cough. Unfortunately, these often don't appear until the disease is advanced, and irreversible lung damage has already occurred. Even then, you may downplay your symptoms, attributing them to aging, being out of shape or the lingering effects of a cold.

But breathing problems usually become progressively worse, and eventually you're likely to get out of breath during routine activities — getting dressed, talking on the phone, even eating. At this point, symptoms are impossible to ignore.

You may also notice other signs and symptoms, including :

  • Fatigue
  • Unexplained weight loss
  • Aching muscles and joints

Pulmonary fibrosis can vary considerably from person to person. Symptoms range from moderate to severe. Some people become ill very quickly, whereas others grow worse over a period of months or years.

Diagnosis:
Diagnosing pulmonary fibrosis can be extremely challenging. The difference between idiopathic and nonidiopathic forms of the disease isn't always clear, and the naming and classification systems for both have historically been confusing and controversial. In addition, many medical conditions, including chronic obstructive pulmonary disease (COPD), asthma and even heart failure, can mimic pulmonary fibrosis, so doctors must rule these out before making a definitive diagnosis.

A complete medical history, physical exam and even a chest X-ray aren't enough to diagnose pulmonary fibrosis. For that reason, you may have tests such as a high-resolution computerized tomography (CT) scan, which provides sharper and more detailed images than conventional CT scans do; an exercise test on a treadmill or stationary bike to monitor your lung function when you're active; and pulmonary function tests to measure how well your lungs work overall.

Often, though, pulmonary fibrosis can be definitively diagnosed only by examining a small amount of lung tissue (biopsy) in a laboratory. The tissue sample may be obtained in one of these ways :

  • Bronchoscopy (transbronchial biopsy). In this procedure, your doctor removes very small tissue samples — generally no larger than the head of a pin — using a small, flexible tube (bronchoscope) that's passed through your mouth or nose into your lungs. The risks of bronchoscopy are generally minor — most often a sore throat and temporary hoarseness from swallowing the bronchoscope — but the tissue samples are sometimes too small for an accurate diagnosis.
  • Bronchoalveolar lavage. In this procedure, your doctor injects saltwater (saline) through a bronchoscope into a section of your lung, and then immediately suctions it out. The withdrawn solution contains cells from your air sacs. Although bronchoalveolar lavage samples a larger area of the lung than other procedures do, it may not provide enough information to diagnose pulmonary fibrosis.
  • Surgical biopsy (video-assisted thoracoscopic surgery). In some cases, your doctor may recommend a surgical biopsy. This is a more invasive procedure in which surgical instruments and a small camera are inserted through two or three small incisions between your ribs. The camera allows your surgeon to view your lungs on a video monitor while removing tissue samples from your lungs. Because video-assisted thoracoscopic surgery doesn't require cutting through a rib, you're likely to have less pain and to heal more quickly than you are with traditional open-lung surgery. Still, because this procedure has a number of risks, it's usually used only when other methods have failed to provide a diagnosis.

Complications :
Complications of pulmonary fibrosis may include :

  • Low blood-oxygen levels (hypoxemia). Because pulmonary fibrosis reduces the amount of oxygen you take in and the amount that enters your bloodstream, you're likely to develop lower than normal blood-oxygen levels. Lack of oxygen can disrupt your body's basic functioning, and severely low levels can be life-threatening.
  • High blood pressure in your lungs (pulmonary hypertension). Unlike systemic high blood pressure, this condition affects only the arteries in your lungs. It begins when the smallest arteries and capillaries are compressed by scar tissue, causing increased resistance to blood flow in your lungs. This in turn raises pressure within the pulmonary arteries. Pulmonary hypertension is a serious illness that becomes progressively worse and may eventually prove fatal.
  • Right-sided heart failure (cor pulmonale). This serious condition occurs when your heart's lower right chamber (ventricle) has to pump harder than usual to move blood through blocked pulmonary arteries.
  • Respiratory failure. This is often the last stage of chronic lung disease. It occurs when blood-oxygen levels fall dangerously low and carbon dioxide levels become too high. Low blood-oxygen levels can lead to heart arrhythmias and unconsciousness; high carbon dioxide levels cause sleepiness and confusion. In either case, respiratory failure may prove fatal.

Treatment:
The lung scarring that occurs in pulmonary fibrosis can't be reversed, and no current treatment has proved effective in halting the progress of the disease or improving quality of life. Still, many people diagnosed with pulmonary fibrosis are initially treated with a corticosteriod (prednisone), sometimes in combination with other drugs that suppress the immune system.

These medications can cause severe side effects, including diabetes, glaucoma, reduced production of red blood cells, skin cancer and lymphoma. For that reason, treatment is usually discontinued if there's no improvement after six months. About one in three people improves temporarily on immunosuppressant drugs, though it's not clear why some people respond and others don't.

Adding high doses — 600 milligrams three times a day — of the natural enzyme N-acetylcysteine to a standard regimen of prednisone and azathioprine helps improve lung function, but it's not clear whether this is because the acetylcysteine is beneficial or because it reduces the toxicity of the other drugs.

Lung transplantation
Lung transplantation may be an option for younger people with severe pulmonary fibrosis who aren't likely to benefit from other treatment options. In order to be considered for a transplant, you must agree to quit smoking if you smoke, be healthy enough to undergo surgery and post-transplant treatments, be willing and able to follow the medical program outlined by therehabilitation and transplant team, and have the patience and emotional strength and support to undergo the wait for a donor organ. The last requirement is particularly important because donor organs are in short supply.

Other treatment approaches
Other pulmonary fibrosis treatments focus on improving quality of life. They include :

  • Oxygen therapy. Using oxygen can't stop lung damage, but it can make breathing and exercise easier, prevent or lessencomplications from low blood-oxygen levels, and improve your sleep and sense of well-being. It can also reduce blood pressure in the right side of your heart. You're most likely to receive oxygen when you sleep or exercise, although some people may use it round-the-clock.
  • Pulmonary rehabilitation. This is a formal program for people with chronic lung disease that includes, but goes far beyond, medical management. The aim of pulmonary rehabilitation is not only to treat a disease or even improve daily functioning, but also to help people with pulmonary fibrosis live full, satisfying lives. To that end, pulmonary rehabilitation programs focus on exercise, on teaching you how to breathe more efficiently, on education, and on emotional support and nutritional counseling.

    Most often, this multifaceted approach requires a team of health care professionals that may include a doctor, nurse, rehabilitation specialist, dietitian and social worker.Programs can vary widely, however. Your doctor can usually tell you about pulmonary rehabilitation programs in your area. Or contact the American Lung Association for more information.

Treatments under investigation
A number of treatments for pulmonary fibrosis are being developed or are in clinical trials. You can find an extensive listing of clinical trials in the National Institutes of Health Clinical Trial Database on the Web. You can also contact the National Heart, Lung, and Blood Institute for more information. If you think you might be interested in participating in a clinical trial, your doctor can help you find an appropriate program.

 
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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