The term interstitial lung disease (ILD), also known as Diffuse Parenchymal Lung Disease (DPLD) comprises more than 200 separate disease entities  that cause progressive scarring of lung tissue. Scarring caused by interstitial lung disease eventually impairs one’s capacity to breathe and absorb adequate oxygen into the bloodstream.. The crude annual incidence of ILDs in India is 10.1–20.2 per 100,000 population.

The pathogenetic sequence involves a series of inflammation and fibrosis that extends beyond disrupting the interstitial bed to changing the parenchyma (alveoli, alveolar ducts, and bronchioles).

Interstitial lung disease is much more likely to affect adults, although infants and children sometimes develop the disorder.

Some of the known cause of ILD include : 

  • Long-term exposure to occupational or environmental agents like mineral dust, organic dust, and toxic gases. Most common are silica, asbestos, coal mine dust. 
  • Allergic reaction to inhaled molds, fungi, bacteria and bits of bird feathers or droppings.
  • Auto immune diseases and connective tissue diseases like rheumatoid arthritis, lupus, systemic sclerosis.
  • Granulomatous diseases like sarcoidosis.
  • Drug induced ILDs.
  • Smoking. Some forms of interstitial lung disease are more common in smokers, and active smoking may aggravate the condition, especially if there is accompanying emphysema.

When the cause of ILD is unidentified, it is labelled as Idiopathic Iinterstitial Pneumonia of which, Idiopathic pulmonary fibrosis is the most common and with a bad prognosis.

In contrast to developed countries, sarcoidosis and Hypersensitivity pneumonitis are the ILDs with the highest burden in India.

The most frequently reported symptom is gradual onset of shortness of breath which is usually progressive, but sometimes it may simply be a persistent cough. Fatigue, chest discomfort, weight loss are other symptoms associated with ILDs. Some patients may be asymptomatic and are incidentally diagnosed on ct scan of the lungs.

ILDs are diagnosed based on history, clinical examination, relevant blood investigations that include auto immune workup, pulmonary function tests, HRCT chest and a lung biopsy as and when required.

Most of the ILDs cause irreversible lung damage and are progressive. Early diagnosis and treatment play a vital role in slowing down the progression of the disease and improving the quality of life.

Treatment for ILD usually focuses on treating underlying disease and improving symptoms.  General supportive measures include smoking cessation, pulmonary rehabilitation which can help improve functionality, and good pulmonary hygiene.

Gastroesophageal reflux disease (GERD) can make ILD worse, hence requires adequate treatment. The mainstay therapy for treatment of ILD is corticosteroids and immunosuppressive therapies to intercept the inflammatory process within the lungs.

Antifibrotic drugs have proven benefits in IPF and other progressive fibrotic ILDs not responding to corticosteroids and other immunosuppressive therapy.

Supplemental oxygen is necessary for those who demonstrate hypoxemia (sao2 less than 88). Pulmonary rehabilitation plays an important role in the management of ILDs.

Unfortunately, despite all the efforts most of the ILDs progress and significantly impair the quality of life.

Vaccination against common pulmonary pathogens is recommended for all patients with ILD irrespective of their age. This will help reducing infectious ecxacerbations and hospitalisations.

When left untreated, idiopathic pulmonary fibrosis (IPF), the prototype of fibrotic ILDs, has a prognosis of 3-5 years survival following diagnosis. Predicting prognosis for individual ILD patients is still difficult. Signs of pulmonary hypertension and right ventricular failure, as well as the presence of a pneumothorax, have been linked to poorer outcomes in ILD.

Lung transplant is the sole treatment modality that can reinstate physiological function in patients with ILD, who worsen despite maximum medical therapy.

No biomarker or clinical prediction algorithm has been identified as a reliable predictor of disease outcome or response to therapy in ILD at this time. As a result, early referral to a lung transplant programme is still suggested to minimise the possibility that a potentially eligible patient would miss out on a lung transplant.


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Views expressed above are the author's own.


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