Asbestos-related lung disease (incl. asbestosis and mesothelioma) Flashcards
When was asbestos banned in the UK?
1999
Name 3 types of diseases caused by asbestos exposure.
- Benign disease - pleural plaques, pleural thickening, benign pleural effusions
- ILD - asbesosis
- Malignancy - mesothelioma, lung cancer.
Define asbestosis.
Asbestosis is a diffuse interstitial lung fibrosis resulting from asbestos fibre exposure. Pleural abnormalities may also result.
Define mesothelioma.
An aggressive epithelial neoplasm arising from the lining of the lung but also abdomen, pericardium, or tunica vaginalis. It is one of the few cancers related directly to an environmental exposure i.e. asbestos.
What types of asbestos fibres are mined commercially?
- Chrysotile (MAIN)
- Crocidolite
- Amosite
- Actinolite
- Anthophyllite
- Tremolite
No differences in disease risk by type.
How common is asbestos-related lung disease?
>100,000 people worldwide die each year from mesothelioma, lung cancer, and asbestosis.
Mesothelioma is still increasing in some European countries and in Japan but has peaked in the USA and Sweden.
The incidence will continue to increase in developing countries.
What pleural abnormalities can also occur in asbestosis?
- calcification
- diffuse pleural thickening
- benign pleural effusions
- rounded atelectasis
NB: these can occur in concordance with or in absence of parenchymal fibrosis
What is the pathophysiology of asbestosis?
Inhaled asbestos fibres (<10µ) deposit at alveolar duct bifurcations → mechanical irritation → alevolitis with macrophages → cytokine release e.g. TNF, IL1beta → fibrosis.
Fibrosis starts at the lower lobes → extensive fibrosis and honeycombing.
Asbestos is cleared by lymphatic drainage and pleural cavities.
Plaques usually occur on parietal pleura.
Those with pleural effusions usually go on to develop diffuse pleural thickening.
Describe the aetiology of mesothelioma.
- Asbestos fibres recruit alveolar macrophages and neutrophils → reactive oxygen and nitrogen species.
- Chronic inflammation and oxidative stress culminate → DNA damage, altered gene expression (proto-oncogenes and tumour suppressor genes) → malignancy.
- Genetic alterations involved: neurofibromatosis type 2 (NF2), BRCA1- associated protein-1 (BAP1), and Cullin 1 (CUL1) genes. Genomic alterations involve loses and gains of chromosome arms.
What are the types of mesothelioma?
Anatomically:
- Pleural (about 90% of mesothelioma cases)
- Peritoneal (5% to 10%)
- Pericardial (<1%)
- Testicular (<1%)
By histological subtype:
- Epithelioid
- Biphasic
- Sarcomatoid
What are the risk factors for asbestos-related disease?
- Asbestos exposure usually before 1980s
- shipyard
- construction
- building maintenance
- brake, floor tile, fireproof textile, insulation production
- family members of those who work in the above industries
- Age 60 to 85yrs
- Male sex (3:1 in mesothelioma)
- Longer duration of exposure
- Smoking → reduced clearance of fibres
What is the key part of the history to establish a diagnosis of asbestos-related lung injury?
Exposure to asbestos that occurred 20 or more years ago
In mesothelioma the latency period is a bit longer at 20-40 years
Describe the clinical features of asbestosis.
- Dyspnoea on exertion
- Cough - dry, non-productive.
- SOB/chest tightness
- Crackles at lung bases
- Clubbing
- If severe:
- Cyanosis
- Decreased chest expansion and breath sounds
- Dullness to percussion
Chest pain not typical, but may raise concerns about mesothelioma.
Describe the clinical features of mesothelioma.
Usually presents with SOB associated with pleural effusion.
- SOB
- Diminished breath sounds - trapped lung/bronchial obstruction of pleural effusion
- Dullness to percussion
- Chest pain
- Cough
- Constitutional symptoms: fatigue, fever, sweats and weight loss.
NB: may present with abdominal distension/pain due to extension to the abdominal cavity with resultant ascites. Often late or peritoneal mesothelioma.
Which investigations would you carry out for asbestosis/mesothelioma?
- CXR (PA and lateral) - shows pleural thickening
- Pulmonary function testing- restrictive or obstructive (esp. if smoker)
- CT chest +/- abdo - more sensitive than CXR
- Lung biopsy - may be done by VATS; rarely needed, unless cancer suspected.
- BAL/thoracentesis - presence of asbestos bodies in lavage fluid or pleural fluid
- PET
Other:
- Immunohistochemistry- positive results for certain markers (e.g., calretinin, keratins 5/6, and nuclear WT1)
- FBC - usually normal; low Hb, high Plt, high WCC usually in advanced disease and are poor prognostic factors
*VATS - video-assisted thoracoscopic surgery
Mesothelioma cannot be diagnosed from imaging alone so thoracentesis or biopsy by VATS needed.
Diffuse pleural thickening
Diffuse pleural thickening and elevated hemidiaphragm
