Interstitial and Occupational Lung Disease Flashcards
What is interstitial disease?
Any disease affecting the lung interstitium (e.g. alveoli, terminal bronchi)
What are the effects of interstitial lung disease?
- Interferes with gas transfer
* Restrictive lung pattern
What are symptoms of interstitial disease?
- Breathlessness (mainly on exertion)
* Dry cough
What are types of interstitial lung disease?
- Acute
- Episodic
- Chronic
What is chronic interstitial lung disease?
- Part of systemic disease
- Exposure to agent (e.g. drug, dust etc)
- Idiopathic - no known cause
What are 3 types of interstitial lung disease?
- Granulomatous diseases e.g. sarcoidosis, extrinsic allergic alveolitis
- Idiopathic pulmonary fibrosis (IPF)
- Non-specific interstitial pneumonia (NSIP)
What is sarcoidosis?
Granulomatous type 4 hypersensitivity disease of unknown cause
What systems are involved in sarcoidosis?
- Common: lungs, lymph nodes, joints, liver, skin, eyes
* Less common: kidneys, brain, nerves, heart
What is the pathology of sarcoidosis?
- Non-caseating granuloma of unknown aetiology
* Imbalance of immune system with type 4 (cell mediated) hypersensitivity
What is unusual about the prevalence of sarcoidosis?
Less common in smokers
What are clinical features of acute sarcoidosis?
- erythema nodosum
- bilateral hilar lymphadenopathy
- arthritis
- uveitis
- parotitis (inflammation of parotid glands)
- fever
What are the clinical features of chronic sarcoidosis?
- lung infiltrates (alveolitis)
- skin infiltrations
- peripheral lymphadenopathy
- hypercalcaemia
- Other organs: renal, myocardial, neurological, hepatitis, splenomegaly
What are differential diagnoses of sarcoidosis?
- Tuberculosis
- Lymphoma
- Carcinoma
- Fungal infection
What are possible investigations for sarcoidosis?
- CXR (BHL) - primary test, often diagnostic
- CT scan of lungs (peripheral nodular infiltrate)
- Tissue biopsy (non-caveating granuloma)
- Pulmonary function (restrictive pattern due to lung infiltrates)
- Blood test - Agiotensin Converting Enzyme (ACE) as activity marker (NOT diagnostic test), hypercalcaemia, increased inflammatory markers)
What is the treatment for acute and chronic sarcoidosis?
- Acute: self-limiting condition - usually no treatment (oral steroids if vital organ affected e.g. impaired lung function, brain, eyes, heart, kidneys)
- Chronic: oral steroids usually needed, immunosuppression (e.g. azathioprine, methotrexate, anti-TNF therapy)
Why do CXR and pulmonary function have to be monitored for several years after sarcoidosis diagnosis?
Often relapses
Why is it important to treat uveitis due to sarcoidosis with steroid drops?
If don’t control uveitis, anterior chamber of eye fills up with inflammatory fluid, leading to glaucoma and long term damage
What are non-caseating granulomas in sarcoidosis composed of?
Epithelioid histiocytes, multinucleate giant cells, lymphocytes, plasma cells, fibroblasts and collagen
What is extrinsic allergic alveolitis (hypersensitivity pneumonitis)?
Type II hypersensitivity (immune complex deposition) reaction to antigen - inflammation of the alveoli
What is another name for extrinsic allergic alveolitis?
Hypersensitivity pneumonitis
What is the aetiology of extrinsic allergic alveolitis?
- Thermophillic actinomycetes (farmer’s lung, malt workers, mushroom workers)
- Avain antigens (bird fancier’s lung)
- Drugs (gold, bleomycin, sulphasalazine)
- No cause identified in 30% of cases
How is hypersensitivity reaction causes in extrinsic allergic alveolitis?
- Immune complexes form
- Circulate in bloodstream
- Become deposited in lungs causing hypersensitivity reaction
What are the 2 classifications of EAA?
Acute or chronic
What are the symptoms of acute EAA?
- Cough
- Breathlessness
- Fever
- Myalgia
When do symptoms of acute EAA normally appear?
Several hours after antigen exposure (flu-like illness)
What are the clinical signs of acute EAA?
- Pyrexia
- Crackles (no wheeze)
- Hypoxia
- On CXR, will see widespread pulmonary infiltrates
What is the treatment for acute EAA?
- Oxygen
- Steroids
- Antigen avoidance
What is chronic EAA?
Repeated low dose antigen exposure over years
What are the symptoms of chronic EAA?
Progressive breathlessness and cough
What are the clinical signs of chronic EAA?
- Crackles
- Finger clubbing (unusual but possible)
- On CXR, will see pulmonary fibrosis, most commonly in the upper zones
- Pulmonary function tests will show low FEV1 and FVC, low gas transfer - TLCO)
What further tests can help diagnose chronic EAA?
- History of exposure
- Precipitins (measure IgG antibodies specific to antigen)
- Lung biopsy
What is the treatment for chronic EAA?
- Remove antigen exposure
* Oral steroids if breathless or low gas transfer
What is Idiopathic Pulmonary Fibrosis?
The most common interstitial lung disease
What is the aetiology of idiopathic pulmonary fibrosis?
Idiopathic However, several possible causes * Imbalance of fibrotic repair system * Possibly related to gastric reflux * IPF NOT an inflammatory disease * More common in smokers
What are other causes of pulmonary fibrosis (other than IPF)?
- Rheumatoid arthritis
- Systemic lupus erythematosus
- Systemic sclerosis
- Asbestos
- Drugs: amiodarone, busulphan, bleomycin, penicillamine, nitrofurantoin, methotrexate
What are the clinical presentations of IPF?
- Progressive breathlessness over several years
- Dry cough
- Finger clubbing
- Bilateral fine inspiratory crackles
- Restrictive pattern on PFTs, reduced lung volume, low gas transfer
- CXR shows bilateral infiltrates
- CT scan - reticulonodular fibrotic shadowing, worse at lung bases and periphery, traction bronchiectasis and honey-combing cystic changes
What are differential diagnoses for idiopathic pulmonary fibrosis?
- Occupational disease (asbestosis, silicosis)
- Connective tissue disease (RhA, scleroderma, Sjogrens Disease, SLE)
- Left ventricular failure
- Sarcoidosis
- Extrinsic allergic alveolitis
How is a diagnosis is idiopathic pulmonary fibrosis reached?
- History (ask about occupation, pets and drug history)
- Examination
- Radiology tests (HRCT scan)
What is done if the presentation or the HRCT scan is atypical in IPF?
Lung biopsy (either transbronchial or thoracascopic) carried out
What is the pathology of idiopathic pulmonary fibrosis?
- Unusual interstitial pneumonia pattern (UIP)
- Heterogenous fibrosis in alveolar walls
- Fibroblastic foci
- Destruction of architecture causing honeycombing
- Very little inflammation as NOT an inflammatory disease
What is the treatment for IPF?
- Steroids and immunosuppressants - do not change course of the disease
- Antifibrotic drugs (Pirfenidone and Nintedanib) - only therapies which have shown to slow down disease progression
- Oxygen if hypoxic
- Lung transplantation in patients under 65
What are the drawbacks of antifibrotic drugs in IPF?
- Antifribotic therapy does not reverse fibrosis, merely slows down progression
- Very expensive
- Many side-effects
What is the prognosis of those with IPF?
Most patients progress into respiratory failure within a few years
What is the median survival of IPF?
4 years after diagnosis
What are the 2 classes of coal workers pneumoconiosis?
- Simple pneumoconiosis
* Complicated pneumoconiosis
What is simple pneumoconiosis?
CXR abnormality - no impairment of lung function, often associated with chronic obstructive pulmonary disease (COPD)
What is complicated pneumoconiosis?
Progressive massive fibrosis - restrictive pattern with breathlessness
What are the causes of chronic bronchitis?
Coal dust + smoking
What are the causes of Caplan’s syndrome?
Rheumatoid arthritis + coal dust, causes pulmonary nodules in lungs
(Also called rheumatoid pneumoconiosis)
What is silicosis?
Occupational lung disease caused by 15-20 years exposure to quarts (e.g. mining, foundry workers, glass workers, boiler workers)
What conditions can exposure to silica (SO2) lead to?
- Simple pneumoconiosis - few symptoms
* Chronic silicosis - restrictive pattern, pulmonary fibrosis
What abnormalities are found on a CXR of someone with simple pneumoconiosis?
Egg-shell calcification of hilar nodes
What is seen on a CXR of someone with complicated pneumoconiosis?
Balls of fibrous tissue that appear like cancer
What is baritosis?
Pneumoconiosis that is caused by long-term exposure to barium dust
What is the appearance of baritosis on a CXR?
Will appear very dense (barium often used for x-ray investigations due to density)
What occupations are most at risk of asbestos-related lung disorders?
Mining, construction, shipbuilding, boilers and piping, automative components (e.g. brake linings)
What is the most common condition caused by asbestos exposure?
Benign pleural plaques (pleural disease)
What are examples of asbestos-related lung disorders?
- Pleural disease - benign pleural plaques, acute asbestos pleuritis, pleural effusion and diffuse pleural thickening, malignant mesothelioma
- Pulmonary fibrosis - “asbestosis”
- Bronchial carcinoma - asbestos multiplies risk in smokers
What is the meaning of “diffuse” when referring to a medical condition?
Not localised - can spread widely
What are examples of pleural disease caused by asbestos exposure?
- Benign pleural plaques - asymptomatic
- Acute asbestos pleuritis - fever, pain, bloody pleural effusion
- Pleural effusion and diffuse pleural thickening - restrictive impairment
- Malignant mesothelioma - incurable pleural cancer
What are clinical presentations of malignant mesothelioma?
Chest pain and pleural effusion
What is the treatment for malignant mesothelioma?
No cure available - chemotherapy can be used to slow down progression, usually fatal within 2 years
What causes asbestosis?
Heavy prolonged exposure to asbestos
What is asbestosis?
Pulmonary fibrosis caused by prolonged asbestos exposure
What are clinical features of asbestosis?
- Diffuse pulmonary fibrosis
- Restrive pattern on PFT
- Asbestos bodies in sputum
- Asbestos fibres in lung biopsy
Why must you be thorough when checking history for asbestos exposure?
Exposure to asbestos may not be obvious - could be a school teacher (school buildings previously riddled with asbestos)
