Interstitial lung disease is an umbrella term to describe conditions that affect the lung parenchyma (the lung tissue) causing inflammation and fibrosis. Fibrosis involves the replacement of the normal elastic and functional lung tissue with scar tissue that is stiff and does not function effectively.
Diagnosis of interstitial lung disease requires a combination of clinical features and high resolution CT scan of the thorax. HRCT shows a “ground glass” appearance with interstitial lung disease. When diagnosis is unclear lung biopsy can be used to take samples of the lung tissue and confirm the diagnosis on histology.
Generally there is a poor prognosis and limited management options in interstitial lung disease as the damage is irreversible. Generally the treatment is supportive and where possible to prevent further progression of the disease. Options are:
- Remove or treat the underlying cause
- Home oxygen where they are hypoxic at rest
- Stop smoking
- Physiotherapy and pulmonary rehabilitation
- Pneumococcal and flu vaccine
- Advanced care planning and palliative care where appropriate
- Lung transplant is an option but the risks and benefits need careful consideration
Idiopathic Pulmonary Fibrosis
This is a condition where there is progressive pulmonary fibrosis with no clear cause. It presents with an insidious onset of shortness of breath and dry cough over more than 3 months. It usually affects adults over 50 years old. Examination can show bibasal fine inspiratory crackles and finger clubbing. Prognosis is poor with a life expectancy of 2-5 years from diagnosis.
Two medications are licensed that can slow the progression of the disease:
- Pirfenidone is an antifibrotic and anti-inflammatory
- Nintedanib is a monoclonal antibody targeting tyrosine kinase
Drug Induced Pulmonary Fibrosis
There are several drugs that can cause pulmonary fibrosis. Key medication that are worth remembering are:
Secondary Pulmonary Fibrosis
Pulmonary fibrosis can occur secondary to other conditions:
- Alpha-1 antitripsin deficiency
- Rheumatoid arthritis
- Systemic lupus erythematosus (SLE)
- Systemic sclerosis
Hypersensitivity Pneumonitis (AKA Extrinsic Allergic Alveolitis)
Hypersensitivity pneumonitis is a type III hypersensitivity reaction to an environmental allergen that causes parenchymal inflammation and destruction in people that are sensitive to that allergen. Bronchoalveolar lavage involves collecting cells from the airways during bronchoscopy by washing the airways with fluid then collecting that fluid for testing. This shows raised lymphocytes and mast cells in hypersensitivity pneumonitis.
Management is by removing the allergen, giving oxygen where necessary and steroids.
Examples of specific causes:
- Bird-fanciers lung is a reaction to bird droppings
- Farmers lung is a reaction to mouldy spores in hay
- Mushroom workers’ lung is a reaction to specific mushroom antigens
- Malt workers lung is a reaction to mould on barley
Cryptogenic Organising Pneumonia
Cryptogenic organising pneumonia was previously known as bronchiolitis obliterans organising pneumonia. It involves a focal area of inflammation of the lung tissue. This can be idiopathic or triggered by infection, inflammatory disorders, medications, radiation or environmental toxins or allergens.
Presentation is very similar to infectious pneumonia with shortness of breath, cough, fever and lethargy. It also presents on similarly to pneumonia on a chest xray with a focal consolidation.
Diagnosis is often delayed due to the similarities to infective pneumonia. Lung biopsy is the definitive investigation. Treatment is with systemic corticosteroids.
Asbestosis is lung fibrosis related to the inhalation of asbestos. Asbestos is fibrogenic, meaning it causes lung fibrosis. It is also oncogenic, meaning it causes cancer. The effects of asbestos usually take several decades to develop. Asbestos inhalation causes several problems:
- Lung fibrosis
- Pleural thickening and pleural plaques
Suffers are eligible for compensation if they develop asbestos related health conditions (except isolated pleural plaques). All patients that die with known exposure to asbestos need to be referred to the coroners.
Last updated March 2019