Interstitial Lung Disease: Types, Causes, Symptoms, And Treatment

Interstitial lung disease (ILD) is a chronic progressive disease that dramatically impacts your lung health and function. Depending on the severity of your symptoms, your medical team will tailor your treatment options to slow disease progression and provide as much comfort as possible.

What is interstitial lung disease?

Interstitial lung disease is a blanket term covering a large group of pulmonary disorders that primarily involve the progressive scarring of your lung tissue. ILD affects the interstitium, which includes the walls of the air sacs of the lungs (alveoli) and the surrounding blood vessels. 

Symptoms appear when the scar tissue impairs your ability to breathe and get enough oxygen to your vital organs. Once lung tissue scarring occurs, the damage is permanent. 

In most cases, treatment for ILD focuses on slowing disease progression rather than curing the current amount of scarring you may have.

What are examples of interstitial lung disease?

Some forms of ILD are idiopathic, which means their cause is unknown. These idiopathic forms include:

• Sarcoidosis¹

• Cryptogenic organizing pneumonia

• Idiopathic interstitial pneumonia

Other types of ILDs are secondary to an identifiable cause. Typically, this is where you’ve had exposure to an occupational or environmental irritant, drug-induced lung toxicity, or radiation-induced lung injury. These include:

• Hypersensitivity pneumonitis²

• Sarcoidosis

• Asbestosis³

• Idiopathic pulmonary fibrosis

What is idiopathic pulmonary fibrosis?

Idiopathic pulmonary fibrosis⁴ (IPF), previously known as cryptogenic fibrosing alveolitis (CFA), is a severe lung condition that causes lung tissue thickening and scarring over time. 

Despite being the most common type of idiopathic interstitial pneumonia, researchers still don’t know what causes this disease to develop. Scientists estimate that idiopathic pulmonary fibrosis affects 13-20 per 100,000 people worldwide.

What are the symptoms of interstitial lung disease?

The primary symptoms of ILD include:

• Difficulty breathing

• Fatigue

• Dry cough

• Loss of appetite

• Depression

• Weight loss

• Rounding (clubbing) of the finger and toenails

What are the complications of interstitial lung disease?

If left untreated, ILD can lead to a variety of life-threatening complications, including:

• Pulmonary hypertension⁵: Increased pressure in the arteries and veins of the lungs results in cardiovascular damage over time.

• Right-sided heart failure⁶: Often due to pulmonary hypertension, increased stress on the heart can force the right ventricle to work harder, eventually leading to heart failure.

• Respiratory failure⁷: During end-stage ILD, respiratory failure can occur due to large amounts of thick scar tissue.

What causes interstitial lung disease?

While healthy lung tissue can heal and respond to injuries, people with ILD develop thick scar tissue in response to irritants. Some of the most common causes of ILD include:

Environmental factors

Long-term exposure to irritants can cause ILD. These include:

• Silica dust

• Asbestos

• Grain dust

• Radiation

• Cigarette smoke

Medications

Many drugs can have side effects that damage lung tissue, including:

• Chemotherapy drugs like bleomycin⁸

• Heart medications like amiodarone⁹ and propranolol

• Antibiotics like nitrofurantoin¹⁰

• Anti-inflammatory medicines like rituximab¹¹ (although rituximab is also an appropriate treatment¹²) and sulfasalazine¹³

Other medical conditions 

Other medical conditions can lead to ILD. Autoimmune/connective tissue diseases cause lung issues, resulting in scar tissue. These conditions include:

• Rheumatoid arthritis

• Scleroderma

• Sarcoidosis

• Sjögren’s syndrome

Idiopathic reasons

In some cases, doctors don’t know what causes ILD.

How is interstitial lung disease treated?

The primary goal of ILD treatments is to slow the progression of scarring while improving your quality of life and comfort. Depending on your specific disease type and symptoms, your primary care provider will work with you to create a personalized treatment plan best suited to you.

Your doctor may prescribe medications to reduce the severity of symptoms, including:

Corticosteroids

If you have an autoimmune disorder, your doctor may prescribe corticosteroids¹⁴ to suppress your immune function to reduce scarring. 

Acid reflux medications

In some cases, you may develop acid reflux symptoms. Taking medications for acid reflux can reduce symptoms and enhance comfort.

Disease-altering medications

Your doctor may prescribe nintedanib¹⁵ or pirfenidone¹⁶ to slow disease progression. These medications have significant side effects, so it’s best to speak with your provider to ensure that this treatment is right for you.

Your healthcare team may explore other treatment options to provide additional comfort after your diagnosis:

• Oxygen therapy to make breathing easier and oxygenation better

• Pulmonary rehabilitation through physical exercise and breathing techniques

• Emotional and mental health support

• Nutritional counseling

If you are not responding well to any of the above treatment options, your doctor may suggest lung transplant surgery. The risks and complications of this procedure can be substantial, so it is best to speak with your care provider to see if this option is right for you.

Clinical trials

In addition to the above treatment options, a care provider may suggest a clinical trial for a new medication or treatment. You can get involved with Pulmonary Fibrosis Clinical Trials (PACT¹⁷) that offer cutting-edge research and treatments, access to leading specialists, extensive medical support, and more.

How is interstitial lung disease diagnosed?

Because there are so many different types of ILD, a doctor may need to order various diagnostic tests to get to the root of your symptoms. These tests can include: 

Blood tests 

Blood work can detect antibodies, autoimmune markers, and signs of increased inflammation in the body that may have links to ILD.

Diagnostic imaging

A doctor can order computerized tomography (CT scans), chest x-rays, and echocardiograms to visualize your lungs and heart. These determine the size and location of scar tissue in the lungs.

Pulmonary function tests

Lung volumes, diffusing capacity, and spirometry tests can determine your current lung function, the severity of respiratory impairment, and breathing patterns.

Bronchoalveolar lavage

A clinician can perform a washing sample (lavage) during a flexible bronchoscopy to obtain samples of cells and fluid from distal airways and alveoli.

Lung tissue biopsy 

A doctor can accurately diagnose pulmonary fibrosis by taking a lung tissue biopsy and sending it to pathology for examination.

When to see a doctor

Due to the nature of the disease, most patients only develop symptoms of ILD once significant scar tissue damage has already occurred. At this point, you will typically present with progressive dyspnea and exercise intolerance. 

If you notice any changes in your breathing function, seek immediate medical care. Getting an early and accurate diagnosis is essential for living a longer life with ILD.

In summary

Interstitial lung disease (ILD) is a generalized term for various chronic and progressive pulmonary conditions that cause significant lung scarring. As a non-curable disease, current treatment for ILD focuses on slowing the progression of the damage. Maintaining regular visits with your primary care provider can increase your chance of early diagnosis.

FAQs

Is interstitial lung disease curable?

Currently, there is no cure for ILD. Research and drug trials continue to push the boundaries of our current levels of care, and modern treatment options for ILD focus on slowing the progression of tissue scarring.

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

The symptoms and severity of ILD can vary from person to person. It also depends on the specific diagnosis. Researchers estimate that people diagnosed with idiopathic pulmonary fibrosis have a median life expectancy of 3-5 years¹⁸.

However, the actual range of survival is broad, with up to 25%¹⁹ of patients living upwards of ten years.

Does COVID-19 cause interstitial lung disease?

Scientists are conducting extensive research to better understand the long-term effects of COVID-19 on our lung health. One study²⁰ found that up to 24% of the group displayed radiographic changes to their lungs (signs of scarring) twelve months after recovering from a COVID-19 infection.

Furthermore, ongoing studies are establishing the exact risk of interstitial lung disease as a sequela (a condition that follows) of COVID-19²¹. Early results demonstrate interstitial lung damage, but whether this will progress to actual ILD is yet to be shown.

What is the difference between COPD and interstitial lung disease?

Chronic pulmonary obstructive disease (COPD) is an inflammatory disorder that causes narrowing and construction of your airway. ILD causes lung tissue to thicken and stiffen, making breathing more difficult over time.

What are the signs of end-stage interstitial lung disease?

During end-stage ILD, you will likely experience profound breathlessness, sometimes paired with depression, heartburn, and weight loss²². Once you reach this stage of the disease, you may require palliative comfort care to manage your symptoms.