Pulmonary Fibrosis Causes

Causes
Pulmonary fibrosis scars and thickens the tissue around and between the air sacs (alveoli) in your lungs. This makes it more difficult for oxygen to pass into your bloodstream. 

The damage can be caused by many different things — including airborne toxins in the workplace, certain lung diseases, radiation directed to cancers in the lung or breast, and even some types of medical treatments.

Radiation treatments

Some 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 was exposed to radiation
• The total amount of radiation administered
• Whether chemotherapy also was used
• The presence of underlying lung disease

Medications

Many drugs can damage your lungs, especially:

• Chemotherapy drugs. Drugs designed to kill cancer cells, such as methotrexate (Trexall) and cyclophosphamide (Cytoxan), can also damage lung tissue.
• Heart medications. Some drugs used to treat irregular heartbeats, such as amiodarone (Cordarone, Nexterone, Pacerone) or propranolol (Inderol , Innopran), may harm lung tissue.
• Some antibiotics. Nitrofurantoin (Macrobid, Macrodantin, others) and sulfasalazine (Azulfidine) can cause lung damage.

Medical conditions

Lung damage can also result from:

• Tuberculosis
• Pneumonia
• Systemic lupus erythematosus
• Rheumatoid arthritis
• Sarcoidosis
• Scleroderma

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.
• Smoking. Far more smokers and former smokers develop pulmonary fibrosis than do people who have never smoked. Pulmonary fibrosis can occur in patients with emphysema.
• Your occupation. You have an increased risk of developing pulmonary fibrosis if you work in mining, farming or construction or if you're exposed to pollutants known to damage your lungs.
• Cancer treatments. Having radiation treatments to your chest or using certain chemotherapy drugs makes you more susceptible to pulmonary fibrosis.
• Genetic factors. Some types of pulmonary fibrosis appear to run in families, so a genetic component is suspected.

Complications

By Mayo Clinic Staff

Complications of pulmonary fibrosis may include:

• 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 and the right ventricle. 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 partially blocked pulmonary arteries.
• Respiratory failure. This is often the last stage of chronic lung disease. It occurs when blood oxygen levels fall dangerously low. Because your lungs are so stiff, like an old dried sponge, it is harder to breathe and that adds to your fatigue and loss of appetite.
• Lung cancer. Long-standing pulmonary fibrosis also increases your risk of developing lung cancer.

Imaging tests

• Chest X-ray. This will usually show the scar tissue typical of pulmonary fibrosis and is useful for following the course of the illness and treatment. Occasionally, the chest X-ray is normal and further tests are required to explain your shortness of breath.
• Computerized tomography (CT). CT scanners use a computer to combine X-ray images taken from many different angles to produce cross-sectional images of internal structures. A high-resolution CT scan can be particularly helpful in determining the extent of lung damage caused by pulmonary fibrosis. Also, some kinds of fibrosis, like silicosis, have characteristic patterns.
• Echocardiogram. A sonogram for the heart, an echocardiogram uses sound waves to visualize the heart. It can produce still images of your heart's structures, as well as videos that show how your heart is functioning. This test can evaluate the amount of pressure occurring in the right side of your heart.

Lung function tests

• Pulmonary function testing. This test requires you to exhale quickly and forcefully through a tube connected to a machine. The machine measures how much air your lungs can hold and how quickly you can move air in and out of your lungs.
• Oximetry. This simple test uses a small device placed on one of your fingers to measure the oxygen saturation in your blood. Oximetry can serve as an easy way to monitor the course of the disease, sometimes more accurately than a chest X-ray can.
• Exercise stress test. An exercise test on a treadmill or stationary bike may be used to monitor your lung function when you're active.

Tissue sample (biopsy)

Often, 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. 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 temporary sore throat and hoarseness from the passage of the bronchoscope — but the tissue samples are sometimes too small for an accurate diagnosis.
• Bronchoalveolar lavage. In this procedure, your doctor injects salt water through a bronchoscope into a section of your lung, and then immediately suctions it out. The solution that's withdrawn 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. Although this is a more invasive procedure with potential complications, it's often the only way to obtain a large enough tissue sample to make an accurate diagnosis. During the procedure, 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. This is done under general anesthesia.

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