Interstitial Lung Disease: A comprehensive review

What is Interstitial Lung Disease?

Interstitial lung disease (ILD) refers to a group of over 200 lung disorders that involve scarring or damage to the interstitium (the tissue and space around the air sacs of the lungs). Normally the interstitium is thin and elastic, but in ILD it thickens and loses its elasticity which makes breathing difficult. Some common forms of ILD include idiopathic pulmonary fibrosis, sarcoidosis, hypersensitivity pneumonitis and collagen vascular disease-associated ILD.

Causes of ILD

The exact causes of ILD are unknown in many cases. However, some potential causes that can trigger ILD include:

- Genetic factors - Certain inherited conditions like Hermansky-Pudlak syndrome or respiratory bronchiolitis-associated Interstitial Lung Disease are risk factors.

- Environmental exposures - Breathing in organic dusts, pollutants, chemical fumes or radiation can damage the lungs over time and cause ILD.

- Autoimmune disorders - Connective tissue diseases like scleroderma or rheumatoid arthritis that affect other parts of the body can also impact the lungs.

- Smoking - Heavy or long-term smoking is linked to some types of ILD like idiopathic pulmonary fibrosis.

- Medications/drugs - Certain medicines have been implicated as causing ILD in rare instances.

- Infections - Some lung infections may trigger chronic interstitial changes.

Symptoms of ILD

Common symptoms of ILD include:

- Dry cough that may be persistent.

- Shortness of breath especially during physical exertion. This tends to worsen over time.

- Fatigue.

- Fingertip swelling or clubbing.

- Weight loss or loss of appetite.

- Chest discomfort or tightness.

Depending on the underlying cause, associated symptoms like joint pain, rash or fever may also be present in some. Severe ILD can impact oxygen levels in the blood.

Diagnosis of ILD

Diagnosing the exact type of ILD requires careful evaluation. Physicians typically obtain a detailed medical and exposure history followed by:

- Pulmonary function tests to assess lung volumes and gas exchange ability. Restrictive patterns are common.

- Chest X-ray or CT scan to detect infiltrates, scarring and changes in lung densities.

- Lung biopsy if needed to examine tissue samples under microscope and confirm findings. Various cell profiles point to specific ILD types.

- Bronchoalveolar lavage to analyze inflammatory cells in lung fluid.

- Antibody blood tests to check for connective tissue disease markers.

Management of ILD

Treatment depends on the underlying cause and stage of ILD. Mild cases may require symptom control only through medications, pulmonary rehabilitation and oxygen therapy. For rapidly progressive forms:

- Corticosteroids like prednisone are commonly used short-term to reduce inflammation, especially in granulomatous ILD like sarcoidosis.

- Immunosuppressants prevent disease progression by modifying the immune system. Common choices are azathioprine, mycophenolate and cyclophosphamide.

- Antifibrotic drugsSlow lung scarring in IPF. Nintedanib and pirfenidone are FDA approved.

- Lung transplantation may benefit select patients with end-stage lung destruction from IPF or other ILDs despite medical therapy.

ILD prognosis depends greatly on early diagnosis and type involved. While certain forms have good long-term outcomes, others tend to worsen progressively over years necessitating aggressive treatment.

ILD encompasses a spectrum of lung disorders that adversely impact the interstitium. Thorough evaluation helps identify the specific cause which guides management. Although some cases have limited treatment options currently, advances in understanding disease mechanisms aid improved diagnosis and targeted therapies. With a multidisciplinary approach and close monitoring, many patients can enjoy stable lung health and quality of life.

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