Asbestos related disease

Background

  • Asbestos is a naturally occuring silicate which was used extensively as chemical/thermal insulation in the construction and ship-building industries in the second half of the 20th century
    • It is now rarely used due to its effect on health
  • Disease severity is often related to both amount and duration of exposure.  There is usually a latent period of years before any disease presents.
  • The generation of people (mainly construction trade workers) exposed to asbestos is now presenting with disease
  • ~2,300 people died of mesothelioma in 2010 (this figure is increasing and is expected to peak around 2016

Pathophysiology

  • After inhalation of asbestos fibres, fibres usually become lodged in the alveolar bifurcations, there is an immune response to the foreign body.  However, the fibres are resistant and remain.  As the immune response continues, fibrosis occurs.
    • This can occur in the alveoli and, in later disease, bronchioles/bronchi- causing a restrictive lung disease (asbestosis)
    • This can also occur in the pleura.  Once fibres enter the alveoli and are phagocytosed they are taken deeper into the interstitium and can reach the pleura.  It is thought that minimal exposure to asbestos by the pleura is enough to cause disease.

Diseases

  • Benign
    • Pleural Plaques
      • Discrete areas of hyaline fibrosis that occur on the parietal pleura of the chest wall, diaphragm, pericardium or mediastinum
      • Almost always asymptomatic; no impairment of lung function
      • Usually benign
      • Identified on X-ray
    • Acute benign asbestos pleurisy and Diffuse pleural thickening
      • ABAP is a common condition of asbestos workers
        • Features include pleuritic chest pain, mild fever, mild SOB/tachycardia
      • DPT affects the visceral pleura and is characterised initially by parenchymal fibrosis/banding and then diffuse thickening of the pleura.  It can occur in up to 1/3 of exposed patients
        • It can cause restrictive lung function, exertional breathlessness, and chest pain (which may be persistent)
        • On X-ray, thickening of the pleura combined with disappearance of the costophrenic angles
          • Occasionally, severe disease can appear a ’round atelectasis’ (infolding of redundant pleura), which may be mistaken for a mass lesion
        • There is no active treatment although surgical pleurodesis/decortication may be an option.  It is important to exclude any cancers including mesothelioma.
  • Asbestosis
    • Diffuse parenchymal lung disease, usually only found in people working with asbestos (high-exposure)
      • Usually quite slow to progress and tends to have a better prognosis than idiopathic restrictive lung disease.  However, respiratory failure and cor pulmonale can occur
      • Lung cancer is common in patients with asbestosis (40%) and mesothelioma can also develop (10%)
    • Usually presents with SOB on exertion and fine, late inspiratory crackles over the lower zones
      • +/- finger clubbing
    • Lung function tests show a restrictive lung defect and HRCT scan shows ground-glass/honeycombing similar to UIP (interstitial lung disease)
      • Biopsy is not required if a history of exposure is present, but histology would show alveolar fibrosis with asbestos bodies (at least 2/cm²)
  • Mesothelioma
    • Malignant tumour of the pleura (or peritoneum) almost exclusively caused by asbestos and can occur many years after exposure.  Prognosis is extremely poor, with an average life-expectancy of around 16 months from diagnosis.
      • Incidence ~1.25/100,000
    • Usually presents as breathless secondary to pleural effusion (can be acute) and/or constant chest pain (chest wall involvement)
      • It can also cause heart failure (pericardial effusion, if involved)
      • Weight loss, fatigue, sweats, finger clubbing may all be present and lymphadenopathy may suggest malignant spread (as might other signs of organ involvement e.g. organomegaly, bone pain/tenderness, GI symptoms
    • CXR/CT may show pleural effusion, pleural thickening, pleural mass (may also show rib destruction from local invasion)
      • Biopsy will confirm disease.  Pleural fluid doesn’t usually provide diagnosis.
    • Management is usually palliative (including chemo-/radio-therapy) although radical surgery may be possible for patients fit for surgery
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