Interstitial lung disease

Interstitial lung disease (ILD), also known as diffuse parenchymal lung disease (DPLD), refers to a group of lung diseases (including idiopathic pulmonary fibrosis), affecting the alveolar epithelium, pulmonary capillary endothelium, basement membrane, perivascular and perilymphatic tissues. The term ILD is used to distinguish these diseases from obstructive airways diseases. Most types of ILD involve fibrosis, but this is not essential; indeed fibrosis is often a later feature. Hence the term pulmonary fibrosis has fallen out of favor.

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Causes

ILD may be classified according to the cause: -

1. Inhaled substances
   • Inorganic
     • Silica
     • Asbestos
     • Beryllium
   • Organic
     • Hypersensitivity pneumonitis
2. Drug induced
   • Antibiotics
   • Chemotherapeutic drugs
   • Antiarrhythmic agents
3. Connective tissue disease
   • Systemic sclerosis
   • Dermatomyositis
   • Systemic lupus erythematosus
   • Rheumatoid arthritis
4. Infection
   • Atypical pneumonia
   • Pneumocystis pneumonia (PCP)
   • Tuberculosis
5. Idiopathic
   • Sarcoidosis
   • Idiopathic pulmonary fibrosis
   • Hamman-Rich syndrome
6. Malignancy
   • Lymphangitic carcinomatosis

Investigation

  Investigation is tailored towards the symptoms and signs. Most patients have blood testing, chest x-ray, pulmonary function testing, and high resolution CT thorax.

Treatment

ILD is not a single disease, but encompasses many different pathological processes. Hence treatment is different for each disease.

If a specific occupational exposure cause is found, the person should avoid that environment. If a drug cause is suspected, that drug should be discontinued.

Many idiopathic and connective tissue-based causes of ILD are treated with prednisolone. Some patients respond to immunosuppressant treatment. Patients with hypoxemia may be given supplemental oxygen.