Asbestos-related lung disease

• What is asbestos-related lung disease?


  Spectrum of pulmonary disorders (inc. benign pleural diseases (pleural plaques, diffuse pleural thickening & asbestos pleurisy) and malignant conditions (lung carcinoma & mesothelioma))

  Arise from exposure to asbestos fibres
• What is the pathophysiology of asbestos-related lung disease?


  Inhalation of asbestos fibres → fibres reach distal airways & lodge in the terminal bronchioles & alveoli → macrophages phagocytose fibres but fail to eliminate them → inflammatory response → fibrosis
• Asbestos can cause a variety of lung diseases from benign pleural plaques to mesothelioma
• What are pleural plaques?


  Benign & do not undergo malignant changes

  Most common form of asbestos-related lung disease

  
• Asbestos exposure can cause diffuse pleural thickening in a similar pattern as empyema or haemothorax.
• What is asbestosis?


  Asbestosis is a chronic lung disease caused by inhaling asbestos fibers, leading to fibrosis (typically in lower lobes) and difficulty breathing.
• Severity of asbestosis is related to length of exposure.
• What are the features of asbestosis?

  Dyspnoea

  Reduced exercise tolerance

  Clubbing

  Bilateral end-inspiratory crackles

  Lung function tests -> restrictive pattern w/reduced gas transfer
• What is mesothelioma?


  Malignant disease of pleura

  Rare & aggressive cancer
• What is shown in the image?

  Mesothelioma

  
• What is shown in the image?

  Pleural plaques

  
• What is the management of pleural plaques?


  Keep an eye on plaques to ensure they don't become an issue (malignancy)
• Pathophys of asbestosis


  Asbestos fibres inhaled → deposit at alveolar duct bifurcation → activate alveolar macrophages → release cytokines (TNF, IL-1b, ROS, RNS) → initiate fibrosis (typically in lower lobes, then tends to progress up) → loss of elasticity → difficulty breathing
• What is shown in the image?

  Asbestosis -> lower zone linear interstitial fibrosis (progressively involves whole lung)

  
• What are the investigations for asbestosis?


  CXR (PA & lateral) -> lower zone linear interstitial fibrosis (progressively involves whole lung)

  CT chest -> more sensitive than CXR

  Pulmonary function tests -> non-specific
• What are the DDx of asbestosis?


  Idiopathic pulmonary fibrosis

  Connective tissue disease

  Hypersensitivity pneumonitis (HP)

  Hard metal lung disease

  Silicosis

  Sarcoidosis

  Medication or radiation-related pulmonary fibrosis
• What are the RFs of asbestosis?


  Asbestos exposure

  Smoking (weak RF)
• What are the signs & symptoms of asbestosis?


  SOB on exertion

  Dry, non-productive cough

  Crackles (initially heard at bases, increases with disease progression)

  Clubbing (advanced)
• What is the treatment & management of asbestosis?


  No treatment to reverse/prevent progression

  Smoking cessation

  Pulmonary rehabilitation -> to reduce symptoms & optimise functional status

  O2 therapy -> pts with low O2 sats

  Lung transplants -> pts with end-stage resp failure

  Pleural decortication -> removal of fibrous tissue or thickened pleura (rare)
• What is mesothelioma?


  Malignant disease of the pleura

  Rare & aggressive cancer
• Pathophys of mesothelioma


  Inhalation of asbestos fibres → fibres resistant to phagocytosis (persist in parenchyma) → lodged fibres cause chronic irritation & inflam of mesothelium → fibrosis

  Asbestos activates macrophages & mesothelial cells → release of ROS & RNS → DNA damage → inflam cytokines released (TNF-a) → promotes cell proliferation → cumulative genetic mutations → uncontrolled cell growth → dysplasia & malignant transformation → locally invasive → may travel to distant organs (contralateral lung, liver, adrenal glands, kidneys) via lymph/blood
• What are the investigations of mesothelioma?


  CXR -> unilateral pleural effusion, irregular pleural thickening, reduced lung volumes and/or parenchymal changes related to asbestos

  CT of chest & upper abdomen -> pleural thickening, pleural and/or pericardial effusion, enlarged hilar and/or mediastinal lymph nodes

  Pleural biopsy
• What is shown in the image?

  CXR of mesothelioma

  
• What is shown in the image?

  CT of mesothelioma

  
• What happens when a CXR has findings suggestive of mesothelioma?


  2 week wait referral
• What are the DDx of mesothelioma?


  Benign reactive mesothelial hyperplasia

  Benign asbestos-related pleural reactions

  Non-small cell lung cancer

  Small cell lung cancer

  Metastatic cancer
• What are the RFs for mesothelioma?


  Asbestos exposure

  Age 60-85 (due to latency period between exposure & development of malignant mesothelioma)

  Male

  Radiation exposure

  Genetic predisposition (FHx)

  Smoking
• What are the signs & symptoms of mesothelioma?


  SOB

  Weight loss

  Fever

  Night sweats

  Chest wall pain

  Clubbing

  Cough

  Diminished breath sounds

  Dullness to percussion
• What is the treatment & management of mesothelioma?


  No standard treatment

  Chemotherapy/immunotherapy -> to improve QoL & survival

  Surgery (if operable)
• Mesothelioma has a poor prognosis. Mean survival = 12 months