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Idiopathic pulmonary fibrosis

IPF, Fibrosing alveolitis, cryptogenic, Familial idiopathic pulmonary fibrosis, Fibrocystic pulmonary dysplasia, Fibrosing alveolitis, Cryptogenic fibrosing alveolitis, Idiopathic fibrosing alveolitis, chronic form, Usual interstitial pneumonia

Overview

Idiopathic pulmonary fibrosis (IPF) is a condition in which tissues in the lungs become thick and stiff, or scarred, over time. The lungs then lose their ability to move oxygen to the brain and other parts of the body. Common symptoms include shortness of breath and a dry, hacking cough. In some cases fibrosis happens quickly, while in others, the process is much slower. Sometimes the disease stays the same for years. The condition is 'idiopathic' because the cause is unknown. When multiple family members are affected, it is called familial IPF. Many people with this condition live for about 3-5 years after the diagnosis. The most common cause of death is respiratory failure.

Symptoms - Idiopathic pulmonary fibrosis

Signs and symptoms of pulmonary fibrosis may include:

  • Shortness of breath (dyspnea)
  • A dry cough
  • Fatigue
  • Unexplained weight loss
  • Aching muscles and joints
  • Widening and rounding of the tips of the fingers or toes (clubbing)

The course of pulmonary fibrosis — and the severity of symptoms — can vary considerably from person to person. Some people become ill very quickly with severe disease. Others have moderate symptoms that worsen more slowly, over months or years.

Some people may experience a rapid worsening of their symptoms (acute exacerbation), such as severe shortness of breath, that may last for several days to weeks. People who have acute exacerbations may be placed on a mechanical ventilator. Doctors may also prescribe antibiotics, corticosteroid medications or other medications to treat an acute exacerbation.

Causes - Idiopathic pulmonary fibrosis

The cause of IPF is unknown but certain environmental factors and exposures have been shown to increase the risk of getting IPF. Cigarette smoking is the best recognized and most accepted risk factor for IPF, and increases the risk of IPF by about twofold. Other environmental and occupation exposures such as exposure to metal dust, wood dust, coal dust, silica dust, hard metal dust, asbestos fibre, biologic dusts coming from hay dust or mold spores or other agricultural products, and occupations related to farming/livestock have also been shown to increase the risk for IPF. There is some evidence that viral infections may be associated with idiopathic pulmonary fibrosis and other fibrotic lung diseases.
Some people who receive radiation therapy for lung or breast cancer show signs of lung damage months or sometimes years after the initial treatment.

Medications
Many drugs can damage your lungs, especially medications such as:

  • Chemotherapy drugs. Drugs designed to kill cancer cells, such as methotrexate (Trexall, Otrexup, others) and cyclophosphamide, can also damage lung tissue.
  • Heart medications. Some drugs used to treat irregular heartbeats, such as amiodarone (Cordarone, Nexterone, Pacerone), may harm lung tissue.
  • Some antibiotics. Antibiotics such as nitrofurantoin (Macrobid, Macrodantin, others) or ethambutol can cause lung damage.
  • Anti-inflammatory drugs. Certain anti-inflammatory drugs such as rituximab (Rituxan) or sulfasalazine (Azulfidine) can cause lung damage.


Medical conditions

  • Dermatomyositis
  • Polymyositis
  • Mixed connective tissue disease
  • Systemic lupus erythematosus
  • Rheumatoid arthritis
  • Sarcoidosis
  • Scleroderma
  • Pneumonia

 

Many substances and conditions can lead to pulmonary fibrosis. 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. Also, some forms of idiopathic pulmonary fibrosis run in families, and heredity may play a role in idiopathic pulmonary fibrosis.

Many people with idiopathic pulmonary fibrosis may also have gastroesophageal reflux disease (GERD) — a condition that occurs when acid from your stomach flows back into your esophagus. Ongoing research is evaluating if GERD may be a risk factor for idiopathic pulmonary fibrosis, or if GERD may lead to a more rapid progression of the condition. However, more research is needed to determine the association between idiopathic pulmonary fibrosis and GERD.

Prevention - Idiopathic pulmonary fibrosis

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.
  • Sex. Idiopathic pulmonary fibrosis is more likely to affect men than women.
  • 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.
  • Certain occupations. 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 can increase your risk of pulmonary fibrosis.
  • Genetic factors. Some types of pulmonary fibrosis run in families, and genetic factors may be a component.

Diagnosis - Idiopathic pulmonary fibrosis

An earlier diagnosis of IPF is a prerequisite for earlier treatment and, potentially, improvement of the long-term clinical outcome of this progressive and ultimately fatal disease. If IPF is suspected, diagnosis can be challenging but a multidisciplinary approach involving a pulmonologist, radiologist and pathologist expert in interstitial lung disease has been shown to improve the accuracy of IPF diagnosis.

Currently, a diagnosis of IPF requires:

  • Exclusion of known causes of ILD, e.g., domestic and occupational environmental exposures, connective tissue disorders, or drug exposure/toxicity
  • The presence of a typical radiological UIP pattern on HRCT.

In the right clinical setting, it is possible to make the diagnosis of IPF by HRCT alone, obviating the need for surgical lung biopsy.

Recognizing IPF in clinical practice can be challenging as symptoms often appear similar to those of more common diseases, such asthma, chronic obstructive pulmonary disease (COPD) and congestive heart failure. The key issue facing clinicians is whether the presenting history, symptoms (or signs), radiology, and pulmonary function testing are collectively in keeping with the diagnosis of IPF or whether the findings are due to another process. It has long been recognized that patients with ILD related to asbestos exposure, drugs (such as chemotherapeutic agents or nitrofurantoin), rheumatoid arthritis and scleroderma/systemic sclerosis may be difficult to distinguish from IPF. Other differential diagnostic considerations include interstitial lung disease related to mixed connective tissue disease, advanced sarcoidosis, chronic hypersensitivity pneumonitis, pulmonary Langerhan’s cell histiocytosis and radiation-induced lung injury.

Radiology:
Chest X-rays are useful in the follow up routine of IPF patients. Plain chest X-rays are unfortunately not diagnostic but may reveal decreased lung volumes, typically with prominent reticular interstitial markings near the lung bases.

The radiological evaluation through HRCT is an essential point in the diagnostic pathway in IPF. HRCT is performed using a conventional computed axial tomographic scanner without injection of contrast agents. Evaluation slices are very thin, 1–2 mm.

Typical HRCT of the chest of IPF demonstrates fibrotic changes in both lungs, with a predilection for the bases and the periphery. According to the joint ATS/ERS/JRS/ALAT 2011 guidelines, HRCT is an essential component of the diagnostic pathway in IPF which can identify UIP by the presence of:

  • Reticular opacities, often associated with traction bronchiectasis
  • Honeycombing manifested as cluster cystic airspaces, typically of comparable diameters (3–10 mm) but occasionally large. Usually sub-pleural and characterized by well-defined walls and disposed in at least two lines. Generally one line of cysts is not sufficient to define honeycombing
  • Ground-glass opacities are common but less extensive than the reticulation
  • Distribution characteristically basal and peripheral though often patchy.
Histology:

According to the updated 2011 guidelines, in the absence of a typical UIP pattern on HRCT, a surgical lung biopsy is required for confident diagnosis.

Histologic specimens for the diagnosis of IPF must be taken at least in three different places and be large enough that the pathologist can comment on the underlying lung architecture. Small biopsies, such as those obtained via transbronchial lung biopsy (performed during bronchoscopy) are usually not sufficient for this purpose. Hence, larger biopsies obtained surgically via a thoracotomy or thoracoscopy are usually necessary.

Lung tissue from people with IPF usually show a characteristic histopathologic UIP pattern and is therefore the pathologic counterpart of IPF. Although a pathologic diagnosis of UIP often corresponds to a clinical diagnosis of IPF, a UIP histologic pattern can be seen in other diseases as well, and fibrosis of known origin (rheumatic diseases for example). There are four key features of UIP including interstitial fibrosis in a ‘patchwork pattern’, interstitial scarring, honeycomb changes and fibroblast foci.

Fibroblastic foci are dense collections of myofibroblasts and scar tissue and, together with honeycombing, are the main pathological findings that allow a diagnosis of UIP.

Bronchoalveolar lavage:
Bronchoalveolar lavage (BAL) is a well-tolerated diagnostic procedure in ILD. BAL cytology analyses (differential cell counts) should be considered in the evaluation of patients with IPF at the discretion of the treating physician based on availability and experience at their institution. BAL may reveal alternative specific diagnoses: malignancy, infections, eosinophilic pneumonia, histiocytosis X, or alveolar proteinosis. In the evaluation of patients with suspected IPF, the most important application of BAL is in the exclusion of other diagnoses. Prominent lymphocytosis (>30%) generally allows excluding a diagnosis of IPF.

Pulmonary function tests:
Spirometry classically reveals a reduction in the vital capacity (VC) with either a proportionate reduction in airflows, or increased airflows for the observed vital capacity. The latter finding reflects the increased lung stiffness (reduced lung compliance) associated with pulmonary fibrosis, which leads to increased lung elastic recoil.

Measurement of static lung volumes using body plethysmography or other techniques typically reveals reduced lung volumes (restriction). This reflects the difficulty encountered in inflating the fibrotic lungs.

The diffusing capacity for carbon monoxide (DLCO) is invariably reduced in IPF and may be the only abnormality in mild or early disease. Its impairment underlies the propensity of patients with IPF to exhibit oxygen desaturation with exercise which can also be evaluated using the 6-minute walk test (6MWT).

Terms such as ‘mild’, ‘moderate’, and ‘severe’ are sometimes used for staging disease and are commonly based on resting pulmonary function test measurements. However, there is no clear consensus regarding the staging of IPF patients and what are the best criteria and values to use. Mild-to-moderate IPF has been characterized by the following functional criteria:

  • Forced Vital Capacity (FVC) of ≥50%
  • DLCO of ≥30%
  • 6MWT distance ≥150 meters.

Prognosis - Idiopathic pulmonary fibrosis

The long-term outlook (prognosis) for people with idiopathic pulmonary fibrosis is poor, with only 20-30% of affected people surviving at least 5 years after diagnosis. Several factors have been associated with a shortened survival time, including:

  • Older age at diagnosis
  • Extensive cigarette smoking
  • Lower body mass index (BMI)
  • More severe physiologic impairment
  • Greater extent of disease on imaging studies
  • The development of other complications or conditions (eg, pulmonary hypertension, emphysema, and bronchogenic cancer)

The natural history of IPF is not completely understood. While it usually follows a course of progressive deterioration, some people remain stable for extended periods and individual outcomes can vary significantly. Still, long-term survival of IPF is not expected.

It now appears that three potential disease courses exist, but there is not currently a definitive way to predict the course in an affected person. They are:

  • a) slowly progressive disease (the most common);
  • b) disease marked by episodes of acute exacerbations; 
  • c) rapidly progressive disease


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 lower right heart chamber (right ventricle). Some forms of pulmonary hypertension are serious illnesses that become progressively worse and are sometimes 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.
  • Lung cancer. Long-standing pulmonary fibrosis also increases your risk of developing lung cancer.
  • Lung complications. As pulmonary fibrosis progresses, it may lead to complications such as blood clots in the lungs, a collapsed lung or lung infections.

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Treatment - Idiopathic pulmonary fibrosis

The lung scarring that occurs in pulmonary fibrosis can't be reversed, and no current treatment has proved effective in stopping progression of the disease. Some treatments may improve symptoms temporarily or slow the disease's progression. Others may help improve quality of life. Doctors will evaluate the severity of your condition to determine the most appropriate treatment for your condition.

Medication (approved therapies)
Your doctor may recommend newer medications, including pirfenidone (Esbriet) and nintedanib (Ofev). These medications may help slow the progression of idiopathic pulmonary fibrosis. Both medications have been approved by the Food and Drug Administration (FDA). 

Nintedanib can cause side effects such as diarrhea and nausea. Side effects of pirfenidone include rash, nausea and diarrhea.

Researchers continue to study medications to treat pulmonary fibrosis.

Doctors may recommend anti-acid medications to treat gastroesophageal reflux disease (GERD), a digestive condition that commonly occurs in people with idiopathic pulmonary fibrosis.

Oxygen
Using oxygen can't stop lung damage, but it can:

  • Make breathing and exercise easier
  • Prevent or lessen complications from low blood oxygen levels
  • Reduce blood pressure in the right side of your heart
  • Improve your sleep and sense of well-being

You may receive oxygen when you sleep or exercise, although some people may use it all the time. Some people carry a canister of oxygen, making them more mobile.

Pulmonary rehabilitation
Pulmonary rehabilitation can help you manage your symptoms and improve your daily functioning. Pulmonary rehabilitation programs focus on:

  • Physical exercise to improve your endurance
  • Breathing techniques that may improve lung efficiency
  • Nutritional counseling
  • Counseling and support
  • Education about your condition

Lung transplant
Lung transplantation may be an option for people with pulmonary fibrosis. Having a lung transplant can improve your quality of life and allow you to live a longer life. However, a lung transplant can involve complications such as rejection and infection. Your doctor may discuss with you if a lung transplant may be appropriate for your condition.


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