What Is Interstitial Lung Disease (ILD)?

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Medically reviewed by Angela Ryan Lee, MD

Interstitial lung disease (ILD) is a broad term for a group of conditions that cause lung inflammation and/or fibrosis (scarring). Lung damage from ILD can make breathing difficult, leading to symptoms like shortness of breath, dry cough, chest pain, and fatigue.

Over 4.7 million people worldwide live with ILD, including children and adults. There are many causes of ILD, including genetics, autoimmune disorders, certain medical treatments (e.g., radiation), and lifestyle and environmental factors. ILD-related lung damage is irreversible, but treatments such as medications, respiratory therapy, and oxygen therapy can help control symptoms, slow disease progression, and prevent further damage.


There are over 200 types of interstitial lung disease (ILD). While ILDs are a diverse group of lung diseases, they all affect the interstitial space (interstitium)—a network of blood vessels and connective tissues in and surrounding the air sacs of the lungs (alveoli). With ILD, the interstitium becomes stiff and thick, making it harder to move air in and out of your lungs.

Classifying ILDs helps healthcare providers identify the cause and determine the most effective treatment options. ILDs can be classified in several ways, generally based on the cause, symptom severity, and how the disease affects your lung structure and function.

Some of the more common types of interstitial lung disease include:

  • Idiopathic pulmonary fibrosis (IPF): This is the most common type of ILD. Idiopathic pulmonary fibrosis causes progressive scarring of lung tissue with no known cause.

  • Sarcoidosis: An inflammatory disease that causes the formation of granulomas (clusters of inflamed tissue) in the lungs and other organs.

  • Hypersensitivity pneumonitis (HP): This is an inflammatory allergic reaction to inhaled allergens like mold, animal dander, or birth feathers or droppings.

  • Connective tissue disease-associated ILD (CTD-ILD): This is associated with autoimmune diseases, such as rheumatoid arthritis or scleroderma.

  • Pneumoconioses: This is a group of ILDs that develop due to occupational or environmental exposure, such as inhaling harmful mineral dust like silica (silicosis) and asbestos (asbestosis).

Interstitial Lung Disease Symptoms

Symptoms of interstitial lung diseases vary depending on the type of ILD and the severity of the disease. Once lung damage has occurred, symptoms may appear suddenly or develop gradually. As the disease progresses, symptoms tend to worsen over time.

Common symptoms of ILD include: 

  • Shortness of breath: The most common symptom of ILD, shortness of breath, is especially noticeable during physical activity or exertion. For example, you may take rapid and shallow breaths while climbing the stairs or feel you can't get enough air during exercise.

  • Chronic cough: A persistent cough (with or without mucus/phlegm) is common with ILD. You may notice your cough has a pattern, worsening at certain times of the day or night, such as first thing in the morning.

  • Chest discomfort: Chest discomfort, such as tightness or heaviness on your chest, is common in people with ILD. Some research suggests that chest discomfort or pain increases as the disease progresses and lung function declines.

  • Fatigue: Up to 95% of people with ILD experience fatigue or excessive tiredness that interferes with day-to-day activities and quality of life.

  • Weight loss: People with ILD may experience loss of appetite and subsequent weight loss. This is especially common as the disease progresses.

  • Clubbing: As your lungs struggle to absorb enough oxygen, blood oxygen levels can decrease and lead to clubbing, the abnormal curving of fingernails and toenails, and enlargement of the fingertips or toes.

  • Abnormal lung sounds: As you breathe, your lungs may make abnormal sounds, such as wheezing (high-pitched sounds) or crackles.

What Causes ILD?

The interstitium is a thin layer of connective tissue that supports your lungs' alveoli (air sacs). Normally, the alveoli stretch and expand as you breathe in oxygen-rich air, which passes through the alveoli walls and into your bloodstream for delivery to your body's tissues and organs. Carbon dioxide then enters the alveoli, which you expel as you exhale.

With interstitial lung disease, inflammation causes fibrosis (scarring), and the alveoli walls become thick and stiff, making it harder to move oxygen and carbon dioxide in and out of your lungs. As the disease progresses, inflammation can cause further damage and limit lung function.

In many cases, the cause of lung damage and ILD is unknown (idiopathic). Known causes of interstitial lung disease include: 

  • Exposure to harmful substances: Inhalation of harmful toxins (especially continual exposure), such as asbestos, silica dust, mold, or allergens (e.g., pet dander).

  • Autoimmune diseases: Autoimmune diseases occur when the immune system mistakenly attacks the body's tissues, leading to chronic inflammation that can damage the body's tissues. Autoimmune conditions linked to ILD include rheumatoid arthritis, scleroderma, dermatomyositis, sarcoidosis, inflammatory bowel disease (IBD), and lupus.

  • Medications and medical treatments: Certain cancer treatments, including chemotherapy drugs and radiation therapy to the chest, antiarrhythmics (for treating irregular heart rates) and certain antibiotics (e.g., nitrofurantoin).

  • Infections: Viral, bacterial, or fungal infections that cause lung fibrosis (scarring) can lead to ILD. Epstein-Barr virus, cytomegalovirus (CMV), and COVID-19 are viruses linked to ILD development. 

Risk Factors

Certain lifestyle, environmental, and genetic factors can increase your risk of interstitial lung disease, including: 

  • Age: The risk of ILD increases with age, with most cases occurring in people ages 50 and older.

  • Smoking: Smoking damages the airways and lungs, significantly increasing your risk of ILD.

  • Genetics: Some types of ILD run in families, and more than ten gene mutations are associated with developing familial interstitial pneumonia, a rare disorder that causes inflammation and scarring of the lung tissue.

  • Underlying conditions: Certain autoimmune and connective tissue disorders, such as rheumatoid arthritis, can increase your risk of ILDs.

  • History of infections: Previous infections, such as tuberculosis, COVID-19, and pneumonia, are associated with a higher risk of ILDs.

  • Occupation or environment: Work involving exposure to harmful dusts (e.g., coal, asbestos) or mold and chemicals increases your risk of lung damage and ILDs.


Interstitial lung disease is diagnosed based on your symptoms, medical history, physical examination, and diagnostic test results. 

When you visit your healthcare provider, they will ask about your personal and family medical history, your current and past occupation, allergies and medications, whether you smoke, or if you have a family member with a history of ILD. 

During the physical examination, your provider will listen to your lungs as you breathe to listen for sounds of wheezing or crackling and may examine your fingers to look for signs of clubbing. They may place a small device called a pulse oximeter on the end of your finger to measure your blood oxygen levels.

Diagnostic tests can help your healthcare provider give an accurate diagnosis. These tests may include blood tests, lung function tests, imaging tests, and/or a lung biopsy.

Blood Tests

Your healthcare provider may order blood tests that include:

  • Complete blood count (CBC) to measure the types and amounts of cells in your blood

  • Metabolic panel to check kidney and liver function

  • Tests that check for markers of autoimmune diseases and infection

  • Arterial blood gas (ABG) that measures your blood oxygen level

Lung Function Tests

Pulmonary (lung) function tests can show how well your lungs work during certain activities, such as exercise and rest. Your healthcare provider may order:

  • Spirometry involves breathing into a mouthpiece connected to a device (spirometer) that measures how much and how quickly you breathe in and out over a certain period.

  • A six-minute walk test involves walking with a heart rate and saturation monitor attached to your body so your healthcare provider can monitor your oxygen saturation (how much oxygen is in your blood) and heart rate while walking.

  • Overnight oximetry records your blood oxygen levels during sleep to help determine whether you need oxygen therapy while you sleep.

Imaging Tests

Imaging tests provide detailed pictures of your lungs, heart, and surrounding tissues. Your healthcare provider may order:

  • Chest X-ray: This test can identify abnormalities like lung fibrosis (scarring) or fluid around your lungs.

  • High-resolution computed tomography (HRCT): This test combines many X-ray photos to provide detailed images of your lung tissues, including the interstitium, to look for abnormalities and determine the extent of lung damage.

  • Echocardiogram: This is an ultrasound that uses sound waves to create pictures of your heart. It can help determine whether ILD is affecting your heart or you have high blood pressure in your lungs' blood vessels—a condition known as pulmonary hypertension.

Lung Biopsy

Your healthcare provider may need to take a small tissue sample (biopsy) from your lungs to provide an accurate diagnosis. They may perform a bronchoscopy, which involves passing a long, flexible bronchoscope tube through your mouth or nose and down your windpipe (trachea) to access your lungs and remove a small tissue sample. The laboratory examines the lung tissue sample under a microscope for signs of inflammation and scarring.

Treatments for Interstitial Lung Disease

While there is no cure for interstitial lung disease or treatment to reverse lung damage, a range of treatment options can help reduce symptoms, prevent or slow disease progression, and improve lung function and quality of life. Your healthcare provider will recommend a treatment plan based on the cause of ILD and the severity of your symptoms.


Medicines can help control lung inflammation and relax your airways to make breathing easier. Your healthcare provider may prescribe:

  • Corticosteroids: Anti-inflammatory drugs, such as prednisone, suppress the immune system and reduce lung inflammation to help prevent further scarring. Your healthcare provider may prescribe oral tablets taken by mouth or an inhaler to breathe in the medicine.

  • Antifibrotics: Antifibrotic drugs, such as Ofev (nintedanib) and Esbriet (pirfenidone), target and block specific cell growth factors that cause lung scarring. They help slow disease progression and lung damage.

  • Immunosuppressants: Immunosuppressant drugs, such as Cellcept (mycophenolate mofetil), Imuran (azathioprine), and Cytoxan (cyclophosphamide), target and suppress certain immune cells to reduce inflammation and prevent further lung damage.

  • Bronchodilators: Inhaled medicines, such as Proair HFA and Proventil HFA (albuterol), relax the airway muscles to open the airways and make breathing easier.

  • Cough suppressants: Depending on the severity of your cough, your healthcare provider may recommend over-the-counter cough drops or medicines such as Robitussin (dextromethorphan) or prescription-strength cough medicine such as Tussionex PennKenetic (hydrocodone) or Tessalon Perles (benzonatate).

Related: Do Cough Syrups or Medications Work?

Oxygen Therapy

If your blood oxygen levels are low and shortness of breath impacts your quality of life, your healthcare provider may prescribe oxygen therapy to ensure your body gets the oxygen it needs. Depending on the severity of your symptoms (e.g., shortness of breath), your healthcare may prescribe continuous oxygen therapy or nocturnal oxygen therapy.

During continuous oxygen therapy, a portable or stationary oxygen concentrator delivers a constant flow of oxygen-enriched air through a nasal prong or a face mask, helping maintain blood oxygen levels throughout the day and night.

If your blood oxygen levels drop while you sleep, nocturnal oxygen therapy can ensure you get adequate oxygen to improve sleep quality and maintain healthy blood oxygen levels during sleep.

Pulmonary Rehabilitation

Pulmonary rehabilitation is an exercise program designed to improve physical function, reduce symptoms, and boost mood and quality of life in people with ILD. A pulmonary rehabilitation program may include exercise training, breathing exercises, mental health management (e.g., anxiety, depression), nutritional counseling, and education on living with ILD.

Lung Transplant

People with advanced or progressive ILD with limited treatment options may qualify for a lung transplant. Lung transplantation involves removing diseased lungs and replacing them with the healthy lungs of a donor.

To be eligible for a lung transplant, you must not have any other major health problems, follow your healthcare provider's instructions, eat a healthy diet, and be mentally, emotionally, and physically prepared to commit to the process of ensuring your transplant is a success.


While it is not always possible to prevent ILD, especially ILDs related to genetics, you can take steps to protect your lung health and lower your risk of developing lung diseases. These steps include

  • Avoid smoking: Smoking destroys healthy lung tissues and causes inflammation in the airways and lungs. If you smoke, talk to your healthcare provider about smoking cessation programs.

  • Limit exposure to harmful substances: If your job involves exposure to toxic chemicals or dusts, talk to your employer about wearing protective equipment. Avoid spending time outdoors days with poor air quality, and consider purchasing an air filter or air cleaner to keep the indoor air in your home safe.

  • Vaccination: Stay up-to-date on recommended vaccinations to protect against respiratory diseases, including pneumonia, influenza, COVID-19, and pertussis (whooping cough).

  • Exercise: Regular physical activity can help keep your lungs strong and healthy and support your overall health.

Related Conditions

People with interstitial lung disease have an increased risk of developing other health problems or complications, especially if ILD goes untreated. These include: 

  • Gastroesophageal reflux disease (GERD): Many people with ILD also have GERD—chronic acid reflux from stomach acids moving into the esophagus. Researchers are currently exploring the connection between the two conditions, though evidence suggests that ILD may cause or worsen GERD symptoms.

  • Lung cancer: Smoking is a risk factor for both ILD and lung cancer, and research suggests people with ILD have an increased risk of lung cancer. Gene mutations (changes) may play a role in this link, though researchers are still exploring the connection between the two diseases.

  • Pulmonary hypertension (PH): PH involves high blood pressure in the arteries to the lungs, often leading to shortness of breath and fatigue. It can develop as a complication in some ILD types, particularly connective tissue disease-associated ILD, due to scar tissue in the lungs' arteries.

  • Respiratory infections: People with ILD have an increased risk of frequent lung infections.

  • Obstructive sleep apnea (OSA): Many people with ILD also have obstructive sleep apnea, in which breathing repeatedly stops and starts during sleep. Researchers are exploring the connection between the two, though weakened breathing muscles and reduced lung capacity may increase your risk of OSA.

Living With ILD

Living with ILD comes with challenges, but there are ways to navigate your journey and enjoy a fulfilling life. Following your treatment plan is the best way to manage symptoms and prevent further lung damage. Talk to your healthcare provider if your symptoms do not improve or seem to worsen.

Coping with a chronic condition like ILD can be emotionally taxing. Open communication with your loved ones and healthcare provider can provide invaluable strength and support, and joining a support group to connect with others with ILD may be a helpful way to learn coping mechanisms and find camaraderie with others who share similar experiences.

Sometimes, you may need to plan activities around your energy levels or use oxygen therapy to help you remain active and engaged in meaningful activities. Staying active is a good way to improve your lung health, manage stress, and maintain a good quality of life.

Frequently Asked Questions

What is the life expectancy of a person with interstitial lung disease?

The average life expectancy for someone with ILD is 3-5 years. Remember that no one can predict your life expectancy, and following your treatment plan is the best way to improve your outcomes.

Is interstitial lung disease a terminal illness?

Interstitial lung disease is a chronic, progressive lung disease that has no cure. While some people die within years after diagnosis, others can live for many years with ILD. Try not to let the diagnosis define your life; by proactively participating in your treatment plan, staying active, and seeking support, you can improve your chances of living for many years.

How quickly does interstitial lung disease progress?

How quickly interstitial lung disease progresses varies, depending on the type of ILD and a person's overall health. While some people face rapidly worsening symptoms, others may live for years by following their treatment plan to slow disease progress and manage symptoms.

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