Interstitial Lung Disease (ILD)

What happens in the lungs

Oxygen passes from the tiny air sacs (alveoli) through a very thin layer of tissue into the blood. In ILD, this layer becomes inflamed, thickened and scarred. The lungs become smaller and stiffer, breathing takes more effort, and oxygen transfer falls, especially during exercise.

Some ILDs are mainly inflammatory and respond well to treatment. Others are mainly fibrotic and tend to progress. Many have a mix.

Types and causes

Idiopathic (no known cause)

• Idiopathic pulmonary fibrosis (IPF): the most common idiopathic form; usually affects people over 60, more often men and former smokers; progressive.
• Nonspecific interstitial pneumonia and other idiopathic interstitial pneumonias.

Connective tissue and autoimmune diseases

• Rheumatoid arthritis
• Scleroderma (systemic sclerosis)
• Myositis (dermatomyositis, polymyositis, antisynthetase syndrome)
• Sjögren's syndrome and lupus

Exposures

• Hypersensitivity pneumonitis: an immune reaction to inhaled organic material such as bird feathers and droppings, mold, hot tubs and moldy hay.
• Occupational dusts: silicosis, asbestosis, coal workers' pneumoconiosis, metal dusts.
• Smoking-related ILDs.

Medicines and treatments

Some chemotherapy drugs, amiodarone, nitrofurantoin, methotrexate, some immunotherapies, and radiation therapy to the chest.

Sarcoidosis

Sarcoidosis causes clusters of inflammatory cells (granulomas) in the lungs and lymph nodes, often with good outcomes.

Genetic

Familial pulmonary fibrosis, including telomere-related disorders.

Symptoms

• breathlessness, at first only with exertion, gradually worsening
• persistent dry cough
• fatigue and reduced exercise ability
• unintended weight loss
• clubbing: rounded, enlarged fingertips with curved nails
• fine "Velcro-like" crackles heard with a stethoscope
• in autoimmune ILD: joint pain, rashes, Raynaud's phenomenon, muscle weakness

Diagnosis

1. Detailed history: occupations, hobbies, pets and birds, home mold, medicines, smoking, family history, autoimmune symptoms.
2. Examination: lung crackles, clubbing, skin and joint signs.
3. Lung function tests: usually show smaller lung volumes (restriction) and reduced gas transfer (DLCO).
4. High-resolution CT scan: the key test; shows the pattern and extent of scarring.
5. Six-minute walk test with oxygen monitoring.
6. Blood tests: autoimmune antibodies, myositis panels, hypersensitivity antibodies.
7. Bronchoscopy with lavage or biopsy, or surgical or cryobiopsy, when the diagnosis is unclear.
8. Multidisciplinary discussion: lung specialists, radiologists and pathologists review findings together, which improves diagnostic accuracy.

Treatment

Remove the cause

Avoid the triggering exposure (for example, birds or mold in hypersensitivity pneumonitis), stop the causative medicine, and stop smoking.

Medicines

• Antifibrotic medicines: nintedanib and pirfenidone slow lung function decline in IPF; nintedanib is also used for other progressive fibrosing ILDs.
• Immunosuppression: steroids, mycophenolate, azathioprine, rituximab or others for inflammatory ILDs, such as those linked to autoimmune disease, hypersensitivity pneumonitis and sarcoidosis. Steroids are not used to treat stable IPF.
• Treatment of acid reflux and other conditions where relevant.

Supportive care

• Pulmonary rehabilitation: supervised exercise and education that improves breathlessness and quality of life.
• Oxygen therapy for low oxygen levels at rest or on exertion.
• Vaccines against flu, COVID-19, pneumococcus and RSV as recommended.
• Cough management and nutrition support.
• Palliative care for symptom relief in advanced disease.

Lung transplant

For selected people with advanced disease who are otherwise fit enough.

Complications

• respiratory failure
• pulmonary hypertension and right heart failure
• acute exacerbations, often life-threatening
• lung cancer (higher risk in IPF)
• collapsed lung and infections

Outlook

The outlook depends heavily on the type. Some ILDs, such as many cases of sarcoidosis and hypersensitivity pneumonitis caught early, improve or stabilize. IPF is progressive, with a historical median survival of about 3 to 5 years from diagnosis, though antifibrotic medicines slow decline and some people live much longer. Regular monitoring with lung function tests guides treatment.

Frequently asked questions

What are the first signs of interstitial lung disease?

The earliest signs are usually breathlessness during exercise or climbing stairs, and a persistent dry cough. These develop gradually, so people often blame age or fitness. A doctor may hear crackles in the lungs, and fingertips may become clubbed.

What causes interstitial lung disease?

Causes include autoimmune diseases such as rheumatoid arthritis and scleroderma, inhaled substances such as bird proteins, mold, asbestos and silica, certain medicines and radiation, and sarcoidosis. In many people, such as those with idiopathic pulmonary fibrosis, no cause is found.

Is interstitial lung disease the same as pulmonary fibrosis?

Not exactly. Interstitial lung disease is the broad group of conditions affecting lung tissue. Pulmonary fibrosis means scarring of the lungs, which occurs in many but not all ILDs. Idiopathic pulmonary fibrosis is one specific type of ILD.

What is the life expectancy with interstitial lung disease?

It varies widely by type. Some forms stabilize or improve with treatment and have a near-normal outlook. Idiopathic pulmonary fibrosis has historically had a median survival of 3 to 5 years, but treatment slows progression and individual outcomes vary.

Can interstitial lung disease be cured?

Most fibrotic ILD cannot be reversed, but treatment can slow progression and ease symptoms. Inflammatory types may improve substantially when the cause is removed or with immune-suppressing medicines. Lung transplant is an option for some people with advanced disease.