Interstitial lung disease: symptoms, causes, stages, treatment and life expectancy

Interstitial lung disease (ILD) is not a single disease. It is a broad term used for a group of conditions that affect the tissue around the lung’s air sacs, causing inflammation, thickening and, in some cases, permanent scarring or fibrosis. As the lung tissue becomes stiff, the lungs may not expand normally and oxygen has more difficulty moving into the bloodstream.

ILD can develop for many different reasons. Autoimmune diseases, certain medications, occupational exposure to dust or chemicals, radiation therapy, environmental allergens and infections can all be associated with different forms of ILD. In some people, no definite cause can be identified. This is known as idiopathic interstitial lung disease, with idiopathic pulmonary fibrosis (IPF) being the most common form.

One of the challenges with ILD is that its course is highly variable. Some forms remain stable for years, while others can progress gradually or more rapidly. This is why an accurate diagnosis and regular monitoring are so important.

What are the common symptoms of interstitial lung disease?

The symptoms of ILD can initially be subtle and may be mistaken for ageing, lack of fitness or another respiratory problem.

The most common symptoms include:

• Shortness of breath, particularly during physical activity
• A persistent dry cough
• Fatigue and reduced stamina
• Chest discomfort
• Reduced ability to exercise
• Unexplained weight loss in more advanced disease
• Loss of appetite
• Low oxygen levels
• Clubbing of the fingers or toes in some patients

As ILD progresses, breathlessness may occur with increasingly less activity and, in severe disease, even while resting. Some patients develop characteristic fine crackling sounds when a doctor listens to the lungs.

Persistent breathlessness or a dry cough should not automatically be assumed to be ILD. Asthma, COPD, heart disease, infections and several other conditions can cause similar symptoms. A proper medical evaluation is therefore essential.

What causes interstitial lung disease?

There are dozens of possible causes of ILD. Broadly, they can be divided into several categories.

Autoimmune and connective tissue diseases

Conditions such as rheumatoid arthritis, systemic sclerosis, lupus and other connective tissue diseases can affect the lungs and lead to ILD.

Environmental and occupational exposure

Repeated exposure to substances such as asbestos, silica, coal dust, metal dust, mould, agricultural dust, chemicals, fumes and bird proteins can cause certain forms of ILD.

Hypersensitivity pneumonitis, for example, can occur after repeated exposure to inhaled organic substances such as mould or bird droppings.

Medications

Several medications have been associated with lung inflammation or fibrosis. Examples include amiodarone, nitrofurantoin, methotrexate, some chemotherapy drugs, daptomycin and certain immune-based cancer treatments.

Radiation therapy

Radiation involving the chest can sometimes cause inflammation or subsequent scarring in lung tissue. The risk depends on factors such as the amount of radiation and the area treated.

Unknown causes

Sometimes doctors cannot identify a clear trigger despite detailed investigation. This is referred to as idiopathic ILD.

Which two drugs are known to cause interstitial lung disease?

There are actually many medications that can cause drug-induced ILD, so limiting the answer to two drugs can be misleading.

Two well-known examples are amiodarone and nitrofurantoin. Amiodarone is used for certain abnormal heart rhythms, while nitrofurantoin is an antibiotic commonly used for urinary tract infections. Other medicines, including methotrexate, bleomycin, some chemotherapy drugs and certain immunotherapies, can also cause lung injury.

Anyone taking these medicines should not stop them without medical advice. If medication-induced ILD is suspected, the treating doctor will assess whether the medicine should be discontinued or replaced.

Is ILD caused by COVID?

COVID-19 can be associated with persistent interstitial lung abnormalities and, in some patients, post-COVID pulmonary fibrosis. However, not every person who has had COVID-19 develops ILD.

Severe COVID-19 pneumonia, particularly when associated with extensive lung injury or acute respiratory distress syndrome (ARDS), can leave persistent abnormalities in the lungs. Studies have described ground-glass changes, organising pneumonia and fibrotic changes following COVID-19, although the long-term course varies considerably. Some patients improve over time, while others have persistent or progressive abnormalities.

Therefore, post-COVID respiratory symptoms require appropriate assessment rather than automatically being labelled as ILD.

How is interstitial lung disease diagnosed?

Diagnosing ILD often requires more than a single test.

Doctors may consider:

• Medical and occupational history
• Medication history
• Family history
• Physical examination
• Chest X-ray
• High-resolution CT (HRCT) scan
• Pulmonary function tests
• Oxygen saturation measurements
• Six-minute walk or exercise testing
• Blood tests for autoimmune conditions
• Bronchoscopy in selected cases
• Lung biopsy in selected cases

HRCT is particularly important because it can show patterns of inflammation and fibrosis and help doctors determine what type of ILD may be present. Pulmonary function tests help assess how well the lungs are working and provide useful measurements for monitoring progression.

In complex cases, ILD may be reviewed by a multidisciplinary team involving pulmonologists, radiologists, pathologists and other specialists.

What are the stages of interstitial lung disease?

Unlike some cancers, ILD does not have one universally accepted stage 1-to-4 staging system that applies to every type.

Doctors instead assess severity and progression using several factors, including:

• Symptoms and exercise tolerance
• Oxygen levels
• Pulmonary function tests, particularly FVC and DLCO
• Findings on HRCT
• Extent of lung fibrosis
• Rate of change over time
• Presence of complications such as pulmonary hypertension

For progressive pulmonary fibrosis (PPF), the 2022 ATS/ERS/JRS/ALAT guideline defines progression in non-IPF ILD using a combination of worsening symptoms, physiological decline and radiological progression over a year, after excluding other explanations.

So when someone asks about the “stage” of ILD, it is more useful to ask how extensive the disease is and whether it is stable or progressing.

What is the final stage of interstitial lung disease?

In advanced ILD, extensive fibrosis can severely impair oxygen transfer and breathing. A person may develop severe breathlessness, persistently low oxygen levels, marked limitation of physical activity and eventually respiratory failure.

Other serious complications can include pulmonary hypertension, heart problems, recurrent lung infections and acute exacerbations.

Advanced ILD may require long-term oxygen therapy, specialist supportive care and, for carefully selected patients, evaluation for lung transplantation.

Is interstitial lung disease curable?

There is no single cure for ILD because ILD represents many different diseases.

Some forms can improve substantially when their underlying cause is identified and treated early. For example, removing an offending environmental exposure or treating an underlying inflammatory or autoimmune condition may prevent additional lung damage.

However, established lung fibrosis is generally not reversible. Treatment is often aimed at controlling inflammation, slowing further scarring, improving symptoms and maintaining quality of life.

This distinction is important: irreversible does not mean untreatable.

What is the best treatment for ILD?

There is no single “best treatment” for every patient. The appropriate treatment depends on the specific ILD, its cause, severity and whether it is progressing.

Treatment may include:

Treating the underlying cause

If ILD is caused by an autoimmune disease, treatment may involve immunosuppressive or immunomodulatory medicines.

If hypersensitivity pneumonitis is caused by a particular exposure, avoiding that exposure is an important part of treatment.

Antifibrotic medicines

For IPF, established antifibrotic medicines include pirfenidone and nintedanib, which can slow the decline in lung function. Nintedanib also has a role in certain patients with progressive pulmonary fibrosis.

Oxygen therapy

Supplemental oxygen may be prescribed when blood oxygen levels are too low.

Pulmonary rehabilitation

Pulmonary rehabilitation can help patients exercise more safely and efficiently, improve physical conditioning and manage breathlessness.

Lung transplantation

For selected patients with severe, progressive disease, lung transplantation may be considered. Referral needs to happen early enough for the patient to undergo appropriate evaluation.

What medications are used to treat interstitial lung disease?

The medication depends on the type of ILD.

Depending on the diagnosis, doctors may use:

• Corticosteroids, such as prednisone, for selected inflammatory forms
• Mycophenolate mofetil
• Azathioprine
• Cyclophosphamide
• Rituximab or other biologic therapies for selected autoimmune-related ILDs
• Pirfenidone for IPF
• Nintedanib for IPF and certain progressive fibrotic ILDs
• Nerandomilast for IPF and progressive pulmonary fibrosis

These medicines are not interchangeable. For example, immunosuppressive treatment that may be appropriate for one inflammatory ILD may not be appropriate for IPF. Treatment should therefore follow a confirmed or strongly suspected ILD diagnosis.

What is the newest treatment for interstitial lung disease?

One of the most important recent developments is nerandomilast (Jascayd).

The U.S. FDA approved nerandomilast for adults with idiopathic pulmonary fibrosis in October 2025 and subsequently approved it for adults with progressive pulmonary fibrosis in December 2025. It is a PDE4 inhibitor that was shown in clinical trials to slow the decline in forced vital capacity (FVC).

This is particularly significant because it represents a new treatment option for progressive fibrotic lung disease. However, availability and regulatory approval can differ between countries, including India, so patients should discuss locally approved options with their pulmonologist.

Can you reverse interstitial lung disease?

It depends on the type.

Inflammation may sometimes improve or resolve, but established fibrosis or scar tissue generally cannot be reversed.

For example, some inflammatory or exposure-related forms of ILD can stabilize or improve after the underlying trigger is removed and appropriate treatment is started. Established fibrotic disease is different: treatment generally aims to prevent or slow further progression rather than remove existing scar tissue.

Does interstitial lung disease always get worse?

No.

ILD behaves differently from one person to another. Some forms remain stable for long periods, some improve with treatment, and others progressively worsen.

Even within the same type of ILD, the rate of progression can vary. This is why regular pulmonary function testing, clinical review and imaging when appropriate are important.

What are some natural treatments for ILD?

There is no natural treatment proven to remove established pulmonary fibrosis. However, healthy lifestyle measures can support overall lung health and help a person cope with chronic respiratory disease.

Useful measures include:

• Avoiding cigarette smoke and second-hand smoke
• Avoiding known occupational or environmental triggers
• Following a balanced, nutritious diet
• Maintaining an appropriate level of physical activity
• Participating in pulmonary rehabilitation when recommended
• Keeping vaccinations up to date as advised by a doctor
• Practising breathing and energy-conservation techniques
• Maintaining a healthy weight
• Getting adequate sleep
• Managing stress and anxiety

“Natural” supplements should not automatically be considered safe or effective. Some can interact with prescription medicines or affect the liver and other organs. Discuss supplements with your doctor before taking them.

Can interstitial lung disease spread?

ILD does not “spread” from person to person like an infection.

However, the disease process within the lungs can progress, causing a larger area of lung tissue to become inflamed or scarred. This is particularly relevant in progressive fibrotic diseases.

The term “spread” can therefore be confusing. ILD is not cancer and does not metastasise to other organs. Instead, some forms can progressively damage more lung tissue.

Can you live a normal life with interstitial lung disease?

Yes, some people with ILD can continue to work, remain active and enjoy many normal activities, particularly when the disease is mild or stable.

The experience varies greatly according to the type of ILD, lung function, symptoms and rate of progression. Some people require very little treatment, while others need oxygen, pulmonary rehabilitation or more intensive medical care.

The goal of treatment is not simply to change a number on a lung function report. It is also to preserve independence, manage symptoms and maintain quality of life.

What is life expectancy with interstitial lung disease?

There is no single life expectancy for ILD.

ILD is an umbrella term covering conditions with very different outcomes. Some people with mild, stable ILD live for many years, while rapidly progressive forms can become life-threatening.

IPF has historically been associated with a median survival of approximately three to five years after diagnosis, but that statistic does not predict an individual patient’s lifespan. The Pulmonary Fibrosis Foundation notes that the three-to-five-year figure is outdated as a simple way of predicting survival because earlier diagnosis and improved treatments mean many people live considerably longer, while others deteriorate much sooner.

Factors affecting prognosis include the specific ILD, age, lung function, oxygen requirements, disease progression, other medical conditions and response to treatment.

Can you live 20 years with IPF?

It is possible for an individual with IPF to live considerably longer than the historical median survival figures, but 20-year survival cannot be assumed or predicted for a particular patient.

IPF has a variable course. Some people experience relatively slow progression, while others develop rapid deterioration or acute exacerbations. Modern antifibrotic treatment and improved supportive care have also changed the management landscape.

A patient’s own pulmonary function trends and clinical course are much more useful than applying a population-level survival statistic.

How long does someone live with interstitial lung disease?

The answer depends primarily on which ILD the person has and whether it is progressing.

There is an enormous difference between mild, stable ILD and rapidly progressive pulmonary fibrosis. Even among patients with IPF, survival varies substantially.

Rather than relying on a fixed number of years, doctors monitor lung function, oxygen levels, exercise capacity, symptoms and CT findings over time. A pattern of change can provide much more meaningful information about an individual’s prognosis.

What is the most common cause of death in patients with interstitial lung disease?

In advanced ILD, progressive respiratory failure is an important cause of death. However, ILD patients can also experience fatal complications such as acute exacerbations, pulmonary hypertension, heart complications and serious infections.

The exact cause of death varies according to the underlying ILD and the patient’s other medical conditions.

What is worse, interstitial lung disease or COPD?

There is no meaningful universal answer to which is “worse.”

ILD and COPD are different groups of lung diseases. ILD primarily affects the lung tissue and can cause restriction and fibrosis, while COPD primarily involves persistent airflow limitation and airway and/or emphysematous changes.

Both can range from mild to severe. Prognosis depends on the specific disease, its severity, complications and how it responds to treatment.

When should you see a doctor?

Persistent breathlessness, unexplained exercise intolerance or a dry cough that does not go away deserves medical attention, particularly if symptoms are gradually worsening.

Early evaluation can help identify potentially treatable causes and establish a baseline for monitoring lung function. Cleveland Clinic notes that earlier treatment may provide a better outlook in appropriate cases.

Seek urgent medical attention for severe or rapidly worsening breathlessness, significant low oxygen levels, confusion, blue lips or sudden deterioration.

Frequently asked questions about interstitial lung disease

Is interstitial lung disease curable?

There is no single cure for ILD. Some inflammatory or exposure-related forms can improve significantly when the underlying cause is treated, but established pulmonary fibrosis is generally irreversible.

What are the common symptoms of interstitial lung disease?

The most common symptoms are shortness of breath and a persistent dry cough. Fatigue, chest discomfort, reduced exercise tolerance, weight loss and low oxygen levels may occur as the disease becomes more advanced.

What is the final stage of interstitial lung disease?

Advanced ILD can result in severe respiratory impairment, low oxygen levels and respiratory failure. Pulmonary hypertension, infections and other complications may also develop.

What is the best treatment for ILD?

There is no single best treatment. Management depends on the type and cause of ILD and may include treating the underlying condition, antifibrotic medicines, immunosuppressive treatment, oxygen therapy, pulmonary rehabilitation and, in selected severe cases, lung transplantation.

What are the stages of interstitial lung disease?

ILD does not have one universal stage 1-to-4 system. Doctors assess severity and progression using symptoms, lung function, oxygen levels, HRCT findings and changes over time.

Which two drugs are known to cause interstitial lung disease?

Amiodarone and nitrofurantoin are two well-known examples, although several other medications can also cause drug-induced lung injury.

What are some natural treatments for ILD?

There is no natural treatment proven to reverse lung fibrosis. Avoiding smoke and known exposures, eating well, staying appropriately active and participating in pulmonary rehabilitation can support overall health and quality of life.

Does interstitial lung disease always get worse?

No. Some forms can remain stable or improve, while others progressively worsen. The course depends on the specific type of ILD.

Can you live 20 years with IPF?

Some people live much longer than historical median survival figures, but 20-year survival cannot be predicted for an individual. IPF has a highly variable course.

What medications are used to treat interstitial lung disease?

Depending on the type of ILD, treatment may include corticosteroids, immunosuppressive or biologic medicines, pirfenidone, nintedanib and, more recently, nerandomilast. Treatment should be individualized.

Can interstitial lung disease spread?

ILD is not contagious and does not spread between people. However, progressive ILD can cause increasing fibrosis within the lungs.

Can you reverse interstitial lung disease?

Existing scar tissue generally cannot be reversed. Some forms of lung inflammation may improve substantially when the underlying cause is treated.

How serious is interstitial lung disease?

ILD ranges from mild and stable disease to severe, life-threatening pulmonary fibrosis. Severity depends on the underlying condition, extent of lung damage and rate of progression.

What is the most common cause of death in patients with interstitial lung disease?

Advanced respiratory failure is an important cause, although acute exacerbations, infections, pulmonary hypertension and cardiovascular complications can also be fatal.

Is ILD caused by COVID?

Severe COVID-19 can be followed by persistent interstitial abnormalities or pulmonary fibrosis in some patients, but most people who have COVID-19 do not necessarily develop chronic ILD.

What is the newest treatment for interstitial lung disease?

Nerandomilast (Jascayd) is a major recent development. The U.S. FDA approved it for adult IPF in October 2025 and for adult progressive pulmonary fibrosis in December 2025.

How long does someone live with interstitial lung disease?

There is no universal life expectancy. The underlying type of ILD, severity, lung function, progression and response to treatment all influence prognosis.

Final thoughts

Interstitial lung disease can sound frightening, particularly when the word “fibrosis” appears on a scan report. But ILD is not one disease, and a diagnosis does not automatically mean that rapid deterioration is inevitable.

The most important steps are identifying the specific type of ILD, looking for a treatable cause, establishing baseline lung function and monitoring whether the disease is stable or progressing. Modern treatment now includes antifibrotic medicines and newer options such as nerandomilast, alongside oxygen therapy, pulmonary rehabilitation and, for selected patients, lung transplantation.

If you have persistent breathlessness or a chronic dry cough, especially if symptoms are getting worse, consult a pulmonologist for an appropriate evaluation rather than trying to determine the cause from symptoms alone.

Medical disclaimer: This article is intended for general health information and does not replace consultation with a qualified doctor. ILD treatment must be individualized according to the underlying diagnosis, lung function, imaging findings and overall health.

To consult a Pulmonologist/Chest Specialist at Sparsh Diagnostic Centre, call our helpline number 9830117733.

#BhaloTheko

Disclaimer:

No content on this site, regardless of date, should ever be used as a substitute for direct medical advice from your doctor or other qualified clinician.