Pneumoconioses

Overview

• Definition
  • inhalation of small dust particles (coni = latin for dust)
• Pathophysiology
  • varied and based on the type of dust
  • fibrogenicity
    • coal (least), asbestos, silica, and beryllium (most)
  • region of respiratory tract involved (and mechanism of clearance) depends on particle size
    • small particles affect alveoli (< 2 microns)
      • phagocytosed by macrophages
    • intermediate particles affect respiratory bronchioles ( > 2 microns but < 10 microns)
      • cleared by mucociliary transport
    • large particles are trapped in the upper respiratory tract
  • all result in interstitial fibrosis
• ↑ incidence of cor pulmonale due to pulmonary hypertension

Coal workers pneumoconiosis (CWP)

• Epidemiology
  • workers of coal mines and inhabitants of large cities
• Pathology
  • affects upper lobes (high ventilation)
  • macrophages phagocytose particles (“dust cells”)
• Sequelae 
  • no association with lung cancer
  • simple CWP
    • like smoking, can produce centrilobular emphysema
    • 1 cm fibrotic centers
  • complicated CWP
    • 1-2 cm fibrotic centers
  • Caplan’s syndrome
• CWP + rheumatoid nodules in lungs

Asbestosis

• Epidemiology
  • workers in shipbuilding, roofing, and plumbing industries
    • asbestos used for insulation
• Pathology
  • affects lower lobes including the entire respiratory unit
  • presence of asbestos bodies (aka ferruginous bodies) 
    • golden-brown fusiform rods (due to iron and protein deposition) 
      • resemble dumbbells → made of iron!
    • located inside macrophages
• Sequelae 
  • calcified pleural plaques in the diaphragm and posterolateral mid lung 
  • ↑ incidence of bronchogenic carcinoma and mesothelioma 
    • bronchogenic carcinoma more common than mesothelioma
    • mesothelioma takes longer time to develop (25-40 years) so is less common
    • smoking has no effect on mesothelium, but amplifies the risk of bronchogenic carcinoma when combined with asbestos
  • no association with TB
• may also result in Caplan’s syndrome

Silicosis

• Epidemiology
  • workers in foundries, sandblasting, and mining industries
• Pathology
  • affects upper lobes
  • macrophages activated by silica (quartz)  
    • release fibrogenic cytokines
  • biopsy shows silica particles (birefringent) surrounded by collagen 
  • “eggshell” calcification of hilar lymph nodes  
• Sequelae
  • may impair macrophage function 
    • ↑ susceptibility to TB
• ↑ incidence of primary lung cancer

Berylliosis

• Epidemiology 
  • aerospace or nuclear industry workers
• Pathology
  • noncaseating granulomas, nodular infiltrates, and enlarged lymph nodes
    • resembles sarcoidosis
• Sequelae
  • ↑ risk for primary lung cancer