Understanding Interstitial Lung Disease: What all You Need to Know

Interstitial Lung Disease

What is Interstitial Lung Disease?

Interstitial lung disease (ILD) refers to a large group of diseases that cause scarring (fibrosis) in the lungs. ILD makes it more difficult for lung tissues to absorb oxygen from the air and release carbon dioxide from the body. The term “interstitial” refers to the spaces between the air sacs (alveoli) in the lungs that are damaged by these diseases. There are over 200 different types of ILD. Some of the more common types include idiopathic pulmonary fibrosis (IPF), hypersensitivity pneumonitis, nonspecific interstitial pneumonia, sarcoidosis, and collagen vascular disease-associated ILD.

Causes of Interstitial Lung Disease
The causes of ILD can be varied. Some known causes include:

- Autoimmune diseases: Connective tissue diseases like scleroderma or rheumatoid arthritis can cause ILD.
- Environmental exposures: Interstitial Lung Diseases Exposure to certain pollutants, chemicals or organic dusts like mold or bird droppings can damage the lungs over time and lead to ILD.
- Genetics: Some forms of ILD, especially IPF, have a genetic component.
- Smoking: Tobacco use is strongly associated with worsening ILD symptoms and progression of disease.
- Infections: Rarely, certain fungal or viral infections can cause pulmonary fibrosis.
- Medications: Some treatments rarely linked to pulmonary toxicity leading to ILD include chemotherapy agents or amiodarone.
- Unknown cause: In many cases, especially IPF, the specific cause is unclear and considered "idiopathic".

Symptoms of Interstitial Lung Disease
Common symptoms of ILD include:

- Shortness of breath (dyspnea): This may only occur with exertion at first but worsens over time.
- Dry cough: Often persistent and non-productive.
- Fatigue: Due to impaired oxygen exchange in the lungs.
- Finger clubbing: Enlargement and soft tissue swelling of the ends of the fingers and toes.
- Dry, raspy sounds in the lungs: Crackles/rales heard on lung exam.
- Decreased lung capacity: Seen on pulmonary function testing.
- Low oxygen levels: Measure on ABG analysis or pulse oximetry.

Diagnosis of Interstitial Lung Disease

To diagnose ILD, doctors obtain a complete medical history and perform a physical exam looking for signs of involvement of other organ systems. Testing used includes:

- Chest x-ray: May show signs of lung scarring but often normal early on.
- High-resolution chest CT: Currently the best imaging modality to identify characteristic patterns.
- Pulmonary function tests: Measure lung volumes and gas exchange. Restrictive or obstructive patterns.
- Lung biopsy: Surgical or bronchoscopic biopsies may be needed to differentiate ILD subtypes by examining tissue samples under a microscope.
- Blood tests: To check for other conditions or organ involvement.

Treatment for Interstitial Lung Disease

Treatment depends on the specific type and severity of ILD but may include:

- Supplemental oxygen: For low oxygen levels to improve symptoms.
- Pulmonary rehabilitation: Breathing exercises and education to maximize lung function.
- Corticosteroids: Immunosuppressants like prednisone can help certain types if not contraindicated.
- Other immunosuppressants: Drugs like azathioprine, mycophenolate or methotrexate slow disease progression.
- Antifibrotic medications: Nintedanib (OFEV) or pirfenidone (ESBRIET) proven to slow decline in IPF.
- Lung transplantation: Considered for selected younger IPF patients with severe impairment.
- Managing exacerbations: With steroids and supportive care during periods of sudden worsening.
- Palliative care: For advanced ILD focused on symptom relief and quality of life near the end of life.
- Vaccinations: Help prevent infections that could exacerbate symptoms.
- Oxygen therapy: For low oxygen levels at rest or during sleep to prolong survival.


Prognosis of Interstitial Lung Disease

The five-year survival rate for ILD ranges widely depending on the specific type from 70-80% for milder types down to 20-40% for severe IPF. Factors that influence prognosis include:

- Type and severity of ILD on presentation and diagnosis.
- Rate of disease progression seen on pulmonary function testing over time.
- Response to treatment and medication tolerance.
- Presence of complicating factors like pulmonary hypertension.
- Age and overall health status and co-morbidities.

Close monitoring by pulmonary specialists is important for managing treatment, following the disease course, and planning for future care options as ILDs can have a variable but often progressively worsening course over months to years without treatment. Research efforts continue towards improved ILD treatment options and one day finding a cure.
 
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