Medicine chapters
Interstitial and occupational lung disease
Diffuse parenchymal lung diseases (idiopathic pulmonary fibrosis, hypersensitivity pneumonitis, drug and connective tissue causes) and the occupational lung diseases (coal, silica, asbestos, cotton, beryllium), with their diagnosis and management.
- Interstitial lung diseases cause progressive breathlessness, dry cough, fine bibasal end-inspiratory crackles and often clubbing, with a restrictive pattern (FEV1/FVC normal or high, low TLC) and low gas transfer (TLCO); HRCT is the key test.
- Idiopathic pulmonary fibrosis (older men, UIP pattern: basal, subpleural honeycombing) is treated with antifibrotics (pirfenidone, nintedanib), not steroids; hypersensitivity pneumonitis (farmer's, bird fancier's lung) needs antigen avoidance and steroids.
- Occupational disease: coal (simple pneumoconiosis, PMF, Caplan), silica (upper lobes, eggshell hilar calcification, TB risk), asbestos (lower-zone fibrosis, pleural plaques, mesothelioma, lung cancer), cotton (byssinosis); management is removal from exposure, smoking cessation and compensation.
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Overview
Interstitial lung diseases (ILDs), also called diffuse parenchymal lung diseases, are a large group of conditions that inflame and scar the alveolar walls and interstitium. They make the lungs small and stiff and impair gas exchange.
Occupational lung diseases are caused by dusts, fumes and antigens at work. In Pakistan, exposures include stone crushing and quarrying (silica), coal mining in Balochistan, textile mills (cotton), sugar mills (bagasse), shipbreaking and old insulation (asbestos), and biomass smoke at home.
The TOS stresses diagnosis and management of occupational lung disease.
Classification
| Group | Examples |
|---|---|
| Known cause: exposures | Pneumoconioses (coal, silica, asbestos), hypersensitivity pneumonitis, radiation |
| Known cause: drugs | Amiodarone, methotrexate, nitrofurantoin, bleomycin, busulfan, cyclophosphamide, paraquat, high-concentration oxygen |
| Connective tissue disease | Systemic sclerosis, rheumatoid arthritis, polymyositis/dermatomyositis, SLE, Sjögren syndrome |
| Granulomatous | Sarcoidosis, hypersensitivity pneumonitis, berylliosis, TB |
| Idiopathic interstitial pneumonias | Idiopathic pulmonary fibrosis (IPF), NSIP, cryptogenic organising pneumonia, smoking-related (DIP, RB-ILD), acute interstitial pneumonia |
| Rare | Langerhans cell histiocytosis (smokers, pneumothorax), lymphangioleiomyomatosis (young women) |
Upper versus lower zone fibrosis
| Upper zone | Lower zone |
|---|---|
| Silicosis, coal (PMF) | Idiopathic pulmonary fibrosis |
| Sarcoidosis (stage 4) | Asbestosis |
| TB | Connective tissue disease (systemic sclerosis, RA) |
| Hypersensitivity pneumonitis (chronic) | Drugs (amiodarone, methotrexate, nitrofurantoin, bleomycin) |
| Ankylosing spondylitis, berylliosis, histiocytosis | Aspiration |
Upper zone "SCHART": Silicosis and Sarcoid, Coal, Hypersensitivity pneumonitis, Ankylosing spondylitis, Radiation, TB. Lower zone is "everything else": IPF, asbestos, connective tissue disease and drugs.
General clinical features
- Progressive exertional breathlessness and a dry cough.
- Fine, bibasal, end-inspiratory ("velcro") crackles.
- Finger clubbing (IPF, asbestosis; not usually in sarcoidosis or HP).
- Cyanosis, then pulmonary hypertension and cor pulmonale late.
General investigations
| Test | Typical finding |
|---|---|
| Spirometry | Restrictive: FEV1 and FVC both low, FEV1/FVC normal or raised (>0.7) |
| Lung volumes | Low TLC |
| Gas transfer (TLCO) | Reduced (often the earliest abnormality) |
| Oxygen saturation | Desaturates on exercise (six-minute walk) |
| Chest X-ray | Reticular or reticulonodular shadowing, small lungs; may be normal early |
| HRCT (key test) | Pattern and distribution: reticulation, honeycombing, traction bronchiectasis, ground glass, nodules |
| Blood tests | ANA, rheumatoid factor, ANCA, myositis antibodies, precipitins (HP), serum ACE |
| Bronchoalveolar lavage | Lymphocytes (HP, sarcoid), neutrophils (IPF), eosinophils, infection, malignancy |
| Lung biopsy | Transbronchial, cryobiopsy or surgical (VATS) when HRCT is not diagnostic |
FEV1 2.0 L, FVC 2.4 L (both below predicted), TLC low, TLCO low
FEV1/FVC = 2.0 ÷ 2.4 = 0.83 → above 0.70, so not obstructive
Low volumes + normal ratio + low TLCO → restrictive defect from lung parenchymal disease (ILD)
A restrictive pattern with a normal or raised KCO (gas transfer per litre of lung) suggests an extrapulmonary cause (obesity, kyphoscoliosis, neuromuscular weakness), not ILD.
Idiopathic pulmonary fibrosis (IPF)
- The commonest idiopathic interstitial pneumonia; progressive and fatal.
- Usually over 60, men more often, smokers or ex-smokers.
- Histology: usual interstitial pneumonia (UIP): patchy subpleural, basal fibrosis with fibroblastic foci and honeycombing next to normal lung.
- HRCT: basal, subpleural reticulation, traction bronchiectasis and honeycombing; in a typical case HRCT avoids the need for biopsy.
- Features: insidious breathlessness, dry cough, clubbing, bibasal crackles; often misdiagnosed as heart failure.
- Treatment:
- Antifibrotic drugs: pirfenidone (photosensitive rash, GI upset) or nintedanib (tyrosine kinase inhibitor; diarrhoea) slow the decline in FVC.
- Steroids and immunosuppression are not used in confirmed IPF.
- Oxygen, pulmonary rehabilitation, treat reflux, vaccines, lung transplant assessment, palliative care.
- Prognosis: median survival about 2–5 years; acute exacerbations carry high mortality; increased lung cancer risk.
IPF is not treated with prednisolone. Antifibrotics (pirfenidone, nintedanib) are the disease-modifying drugs.
Other idiopathic interstitial pneumonias (brief)
| Type | Clue | Steroid response |
|---|---|---|
| NSIP | Younger, often with connective tissue disease; ground glass, little honeycombing | Good |
| Cryptogenic organising pneumonia (COP) | Flu-like illness, migratory peripheral consolidation not improving with antibiotics | Very good (relapses) |
| DIP and RB-ILD | Smokers | Stop smoking |
| Acute interstitial pneumonia (Hamman–Rich) | Rapid ARDS-like respiratory failure | Poor; high mortality |
Hypersensitivity pneumonitis (extrinsic allergic alveolitis)
An immune reaction (type III and type IV) to inhaled organic antigens in the small airways and alveoli. Smokers are affected less often.
| Disease | Exposure | Antigen |
|---|---|---|
| Farmer's lung | Mouldy hay, grain | Thermophilic actinomycetes (Saccharopolyspora rectivirgula, formerly Micropolyspora faeni) |
| Bird fancier's (pigeon breeder's) lung | Pigeons, parrots, budgerigars | Avian proteins in droppings and feather bloom |
| Bagassosis | Mouldy sugarcane fibre (sugar mills) | Thermophilic actinomycetes |
| Malt worker's lung | Mouldy barley | Aspergillus clavatus |
| Mushroom worker's lung | Mushroom compost | Thermophilic actinomycetes |
| Humidifier or air-conditioner lung | Contaminated water | Bacteria, amoebae |
- Acute: fever, chills, cough and breathlessness 4–8 hours after exposure, settling within 1–2 days away from it; fine crackles, inspiratory squeaks.
- Chronic: insidious breathlessness, weight loss, upper and mid-zone fibrosis, sometimes clubbing.
- Tests: serum precipitins (IgG) to the antigen (show exposure, not disease), HRCT (centrilobular nodules, ground glass, air trapping on expiration), BAL lymphocytosis with a low CD4:CD8 ratio, biopsy with poorly formed granulomas.
- Management: avoid the antigen (masks, ventilation, change of job or hobby); prednisolone for persistent or severe disease; established fibrosis does not reverse.
Precipitating antibodies are common in exposed people without disease (e.g. pigeon fanciers). A positive test supports exposure only.
Drug-induced ILD
| Drug | Pattern |
|---|---|
| Amiodarone | Pneumonitis and fibrosis; also thyroid, liver, skin and eye effects |
| Methotrexate | Acute hypersensitivity pneumonitis (fever, cough, infiltrates) |
| Nitrofurantoin | Acute pneumonitis or chronic fibrosis |
| Bleomycin | Dose-limiting pulmonary fibrosis (worse with oxygen) |
| Busulfan, cyclophosphamide | Fibrosis |
Management: stop the drug; steroids for severe pneumonitis.
Occupational lung disease
Pneumoconioses (mineral dusts)
| Disease | Who | Key features |
|---|---|---|
| Simple coal worker's pneumoconiosis | Coal miners | Small rounded opacities graded by the ILO system; few symptoms; dust-filled macrophages (anthracosis) |
| Progressive massive fibrosis (PMF) | Coal or silica, heavier exposure | Large upper-lobe fibrotic masses that may cavitate; black sputum (melanoptysis); mixed obstructive and restrictive defect; can progress after exposure ends |
| Caplan syndrome | Coal (also silica, asbestos) plus rheumatoid arthritis | Multiple rounded lung nodules 0.5–5 cm; rheumatoid factor positive |
| Silicosis | Stone cutters and crushers, quarry workers, sandblasters, foundry workers, potters, glass workers | Highly fibrogenic; upper-zone nodular fibrosis; eggshell calcification of hilar nodes; greatly increased risk of TB (silica damages macrophages); also lung cancer |
| Asbestosis | Shipbuilding and shipbreaking, insulation, roofing sheets, brake linings | Lower-zone fibrosis, clubbing, basal crackles; restrictive defect, low TLCO; asbestos bodies (ferruginous bodies) in sputum or tissue |
| Berylliosis | Aerospace, electronics, alloys | Sarcoid-like non-caseating granulomas and hilar nodes; type IV hypersensitivity; beryllium lymphocyte proliferation test |
| Siderosis (iron), stannosis (tin), baritosis (barium) | Welders, metal workers | Dense shadows on X-ray but benign, little effect on function |
A stone cutter or quarry worker with upper-zone nodules, eggshell hilar calcification and a new cavity has TB until proven otherwise; silica damages macrophages.
Effects of asbestos
| Effect | Points |
|---|---|
| Pleural plaques | Commonest; calcified plaques on parietal and diaphragmatic pleura; benign marker of exposure, no malignant potential |
| Benign asbestos pleural effusion | Within about 20 years of exposure; often recurrent |
| Diffuse pleural thickening | Restrictive defect, breathlessness |
| Asbestosis | Heavy exposure; lower-zone fibrosis |
| Mesothelioma | Pleural (or peritoneal) cancer, even after light exposure; latency 20–40 years; crocidolite (blue asbestos) most dangerous; chest pain, breathlessness, unilateral effusion with pleural thickening; poor prognosis |
| Lung cancer | Commoner than mesothelioma; multiplicative risk with smoking |
Smoking plus asbestos multiplies lung cancer risk far more than either alone; mesothelioma is not linked to smoking.
Airway diseases from work
- Occupational asthma: isocyanates (spray painting), flour (bakers), wood dust, latex, soldering fumes; symptoms improve on days off and holidays; confirm with serial peak flows at and away from work.
- Byssinosis: cotton, flax and hemp dust in textile mills; chest tightness and wheeze worst on the first day back at work ("Monday fever"), easing through the week; chest X-ray normal; chronic exposure causes fixed obstruction.
- COPD from coal, cadmium and other dusts.
Diagnosis of occupational lung disease
- Detailed occupational history: every job in order since school, tasks, materials, duration, protective equipment, symptoms at work versus off work, co-workers affected, hobbies (pigeons) and home exposures.
- Chest X-ray (ILO classification for pneumoconiosis) and HRCT.
- Lung function: restrictive with low TLCO (fibrosis); obstructive and variable (occupational asthma); serial peak flows at and away from work.
- Specific tests: precipitins (HP), BAL, beryllium lymphocyte proliferation test, sputum for AFB in silicosis, biopsy or pleural biopsy (mesothelioma).
Management of occupational lung disease
- Remove or reduce exposure (the most important step): job change, dust suppression, wet cutting, ventilation, enclosure, respirators; regulation and screening of workers.
- Stop smoking (especially with asbestos exposure).
- There is no specific cure for pneumoconiosis; fibrosis does not reverse.
- Screen silicosis patients for TB and treat latent or active TB.
- Steroids for hypersensitivity pneumonitis and berylliosis.
- Supportive: bronchodilators, pulmonary rehabilitation, long-term oxygen for hypoxaemia, vaccines, treat cor pulmonale; lung transplant in selected patients.
- Mesothelioma: chemotherapy, pleural drainage and pleurodesis, palliative care.
- Compensation: these are prescribed occupational diseases in many countries; document exposure carefully. In Pakistan, workers' compensation and labour laws apply; check current provincial rules.
Expect: restrictive spirometry (normal or high FEV1/FVC, low TLC and TLCO), HRCT as the key test, IPF with UIP pattern, clubbing and basal crackles treated with pirfenidone or nintedanib rather than steroids, upper versus lower zone causes, farmer's lung and bird fancier's lung with precipitins and antigen avoidance, bagassosis in sugar mill workers, drug causes (amiodarone, methotrexate, nitrofurantoin, bleomycin), coal worker's pneumoconiosis, PMF and Caplan syndrome, silicosis with eggshell calcification and TB risk in stone cutters, asbestos causing lower-zone fibrosis, pleural plaques, mesothelioma after 20–40 years and lung cancer multiplied by smoking, byssinosis with Monday symptoms, berylliosis mimicking sarcoid, and removal from exposure as the main management.
Quick revision
- ILD: dry cough, breathlessness, velcro crackles, clubbing; restrictive, low TLCO; HRCT.
- IPF: older men, UIP, basal subpleural honeycombing; pirfenidone or nintedanib; no steroids.
- HP: antigen 4–8 h before symptoms; precipitins; avoid antigen, steroids.
- Drugs: amiodarone, methotrexate, nitrofurantoin, bleomycin.
- Silicosis: upper zone, eggshell nodes, TB risk.
- Coal: simple CWP, PMF (black sputum), Caplan with RA.
- Asbestos: plaques (benign), asbestosis (lower zone), mesothelioma (20–40 years), lung cancer with smoking.
- Byssinosis: cotton, first day back at work. Berylliosis: sarcoid-like.
- Main treatment of occupational disease: stop the exposure.
Written by The House Job from standard references (Kumar and Clark's Clinical Medicine).
FAQ
What lung function pattern does pulmonary fibrosis cause?
A restrictive pattern: reduced FEV1 and FVC with a normal or raised FEV1/FVC ratio, low total lung capacity and a reduced gas transfer factor.
Why are silicosis patients at risk of tuberculosis?
Silica particles are toxic to alveolar macrophages, which are the main defence against M. tuberculosis, so TB is much commoner and should be screened for.
Are pleural plaques dangerous?
No. They are benign markers of asbestos exposure and do not turn malignant, but they show that the person is at risk of mesothelioma and lung cancer.
Are steroids used in idiopathic pulmonary fibrosis?
No. Steroids and immunosuppressants are not recommended in confirmed IPF; pirfenidone or nintedanib are used to slow the fall in lung function.