Interstitial lung disease
- Generic term used to describe a number of conditions that primarily affect the lung parenchyma in a diffuse manner
- They are characterised by chronic inflammation and or progressive fibrosis and share a number of clinical and pathological features
Clinical features
- Dyspnoea on exertion
- Non productive cough
- Abnormal breath sounds
- Restrictive spirometry
Pathological features
- Fibrosis and remodelling of the interstitium
- Chronic inflammation
- Hyperplasia of type II pneumocytes
Classification;
- Those with a known aetiology;
- Occupational/environmental – asbestosis, berylliosis, silicosis
- Drugs – nitroflurantoin, bleomycin, amiodarone, sulfasalazine, busulfan
- Hypersensitivity reactions – extrinsic allergic alveolitis
- Infections – TB, fungi, viral
- Occupational/environmental – asbestosis, berylliosis, silicosis
- Those associated with systemic disorders;
- Sarcoidosis
- RA
- SLE, systemic sclerosis, mixed CT diseases, Sjogren’s syndrome
- UC, renal tubular acidosis, autoimmune thyroid disease
- Sarcoidosis
- Idiopathic
- Idiopathic pulmonary fibrosis (IPF)/cryptogenic fibrosing alveolitis
- Cryptogenic organising pneumonia
- Lymphocytic organising pneumonia
- Idiopathic pulmonary fibrosis (IPF)/cryptogenic fibrosing alveolitis
Extrinsic allergic alveolitis
- In sensitized people, inhalation of allergens (fungal spores or avian proteins) provokes a hypersensitivity reaction
- In the acute phase, the alveoli are infiltrated with acute inflammatory cells
- With the chronic phase, granuloma formation and obliterative bronchiolitis occur
Causes;
- Bird fanciers and pigeon fanciers lung
- Farmers and mushroom workers lung
- Malt workers lung
- Bagassosis
Clinical features
- 4-6hr post-exposure
- Fever, rigors, myalgia, dry cough, crackles
- Chronic
- Increasing dyspnoea, weight loss, exertional dyspnoea, type I respiratory failure, cor pulmonale
Tests
- Acute
- Bloods – raised neutrophils, raised ESR, positive serum precipitans (indicates exposure only)
- CXR – mid-zone mottling/consolidation, hilar lymphadenopathy
- Lung function tests – reversible restricted defect
- Chronic
- Bloods – positive serum precipitans
- CXR – upper zone fibrosis, honey comb lung
- Lung function tests – persistent changes
- BAL – increased lymphocytes and mast cells
Management
- Acute attack- remove allergen, give oxygen. Give oral prednisolone 40mg/24hr
Idiopathic pulmonary fibrosis
- Inflammatory cell infiltrate and pulmonary fibrosis of unknown cause
- Also known as cryptogenic fibrosing alveolitis
- The commonest cause of interstitial lung disease
Symptoms
- Dry cough, exertional dyspnoea, malaise, weight loss, arthralgia
Signs
- Cyanosis, finger clubbing, fine end inspiratory crackles
Complications
- Type I respiratory failure
- Increased risk of cancer
Tests
- Bloods
- ABG, raised CRP, Ig ANA
- CXR – decreased lung volume, bilateral lower zone reticular nodular shawdowing, honeycomb lung
- Spirometry – restrictive
- BAL – increased lymphocytes (good response), or neutrophils and eosinophils (poor response)
- Lung biopsy
Management
- A large proportion have chronic irreversible disease unresponsive to treatment
- Prednisolone 0.5mg/kg/24hr for 4 wk then 0.25mg/kg/24hr for 48wk
- Monitor response via symptom enquiry, CXR and lung function tests
- May consider lung transplantation
Prognosis
- 50% 5 yr survival rate
Interstitial dust diseases
Coal workers pneumoconiosis (CWP)
- Inhalation of coal dust particles
- Ingested by macrophages which die releasing their enzymes which are fibrotic
- Clinical features
- Asymptomatic but co-existing bronchitis is common
- CXR may show round opacities especially in upper zone
- Progressive massive fibrosis (PMF) is due to progression of CWP which causes progressive dyspnoea, fibrosis and eventually cor pulmonale
- CXR – upper zone fibrotic masses
- Caplan’s syndrome is the association between RA, pneumoconiosis and pulmomary rheumatoid nodules
Silicosis
- Inhalation of silica particles which are very fibrinogenic
- Clinical features;
- Progressive dyspnoea, increased incidence of TB, CXR shows diffuse military or nodular pattern in upper and mid-zones and egg shell calcification of hilar nodes
Asbestosis
- Causes by inhalation of asbestos fibers
- Chrysotile (white asbestos) is the least fibrogenic, crocidolite (blue asbestos) is the most fibrogenic
- Clinical features;
- Progressive dyspnoea, clubbing, fine inspiratory crackles. Also causes pleural plaques, increased risk of bronchial adenocarcinoma and mesothelioma
Malignant mesothelioma
- Tumour of the mesothelial cells, usually occurs in the pleural and rarely in the peritoneum or other organs
- Clinical features
- Chest pain, dyspnoea, weight loss, finger clubbing, pleural effusions
- If tumour has metastasized there may be lymphadenopathy, hepatomegaly, bone pain, abdominal pain/obstruction
- Test
- CXR/CT – pleural thickening
- Diagnosis is made on pleural biopsy
- Prognosis is very poor, less than 2 years