• Miners inhaling quartz (silica) or coal dust
  
• Radiography of silicosis and CWP are similar:
  
  • Simple: micronodules < 1 cm, upper lungs, hilar/mediastinal lymphadenopathy, egg shell calcifications
    
  • Complicated known as progessive massive fibrosis (PMF): aggregation of nodules into large masses, may cavitate
    
  • As PMF worsens profusion of nodules decreases
    
  • Acute silicoproteinosis: resembles alveolar proteinosis, progresses to fibrosis
    
  • Caplans syndrome: CWP + rheumatoid arthritis + necrobiotic nodules
    
• Silicosis: round lamellated collagen surrounding silica particles
  
• CWP: coal macule composed of black pigmented macrophages in respiratory brnochioles
  
• Increased risk for TB
  
• Requires 20 or more years of high dust exposure, silicosis will progress, even after removal from dust in contrast to CWP
  
• Increased mortality with PMF

Chest radiography

• Findings seen 10 to 20 years after exposure
  
• Silicosis and CWP similar, usually less severe in CWP
  
• Simple silicosis
  
  • 1 – 3 mm nodules, posterior segments, upper lobes
    
  • Nodules may calcify
    
  • Reticular opacities
    
  • Nodules increase in size and number and may eventually involve all lobes
    
  • Hilar and mediastinal lymphadenopathy, egg shell calcification
    
• Complicated silicosis (PMF)
  
  • Nodules coalesce and are > 1 cm
    
  • Usually bilateral, right > left
    
  • Usually located in dorsal aspect of lung
    
  • PMF may be lens shaped (wide PA and narrow lateral view)
    
  • Overall profusion of nodules decreases due to aggregation into PMF
    
  • May have foci of amorphous calcification, or calcified rim
    
  • Migrates centrally with time
    
  • May cavitate
    
  • Lung distal to PMF emphysematous
    
    • Risk for spontaneous pneumothorax
      
• Acute silicoproteinosis
  
  • Butterfly edema pattern
    
  • Air bronchograms
    
  • Hilar/mediastinal lymphadenopathy
    
  • Progresses rapidly over months
    
  • Fibrosis, distortion, bullae, pneumothorax
    
• Caplan’s syndrome
  
  • Multiple large nodules (may cavitate)
    
  • Nodular interstitial thickening (CWP)
    
  • Bone changes of rheumatoid arthritis
    
    • Humeral or clavicular erosions
      

CT/HRCT

• HRCT – best imaging modality
  
• Can detect disease with normal radiograph
  
• Micronodules
  
  • Upper lobe and posterior segment predominance
    
  • Location in center and periphery of lobule
    
  • < 7 mm diameter
    
  • May calcify
    
• Aggregation of nodules into PMF more readily detected
  
• PMF
  
  • Lens shaped
    
  • Nodules > 7 mm
    
  • May cavitate,
    
  • Migrate to hila with time
    
  • May have punctate calcification
    
  • Lung distal to PMF emphysematous
    
• Hilar/mediastinal lymphadenopathy, egg shell calcification,

• Sarcoidosis
  
• TB
  
• Fungal infection
  
• Langerhans cell histiocytosis
  
• Hypersensitivity pneumonitis
  
• Differentiation
• History of occupational exposure
  
• Egg shell calcification only seen with sarcoid
  
• Langerhans cell histiocytosis or Farmers lung do not lead to PMF

• General
  
  • Upper lobe predominance
    
  • Increased risk of tuberculosis
    
  • Silica more fibrogenic
    
  • Progressive massive fibrosis - nodules aggregate, form small and large masses of fibrosis, sometimes with cavitation
    
• Silicosis
  
  • Inhalation of silica dust, silicon dioxide (SiO2)
    
  • Silica particles within concentric lamellae of collagen in bronchioles, small vessels, and lymphatics
    
  • Birefringent silicate crystals (1 – 3 µ) in nodules by polarized microscopy
    
  • Silica laden macrophages carry particles to hilar and mediastinal nodes and form granulomas
    
  • May co-exist with TB
    
  • Silicoproteinosis high concentrations of silica, alveolar filling by lipoproteinaceous material, similar to alveolar proteinosis
    
• Coal workers pneumonconiosis
  
  • Macule: stellate shaped collection of macrophages containing black particles, (1 – 5µ) in terminal and respiratory bronchioles and in pleural lymphatics
    
  • No or little fibrosis

• More common in men with occupational history of exposure
  
• Silicosis progressive, even after removal from dust
  
• CWP will not prgoress is removed from dust
  
• Sandblasting, work in quarries, mining, glassblowing, pottery making
  
• Silica often found in coal mines (silica most common element earth’s crust)
  
• Acute silicoproteinosis
  
  • Massive exposure to silica dust
    
  • Usually seen in sandblasters
    
  • Marked cellular and exudative alveolar reaction
    
• Chronic form requires 20 or more years of high dust exposure
  
• Caplan’s Syndrome
  
  • CWP, rheumatoid arthritis, necrobiotic lung nodules
    
• Symptoms
  
  • None with simple silicosis.
    
  • Miners commonly smoke and have symptoms related to bronchitis or emphysema
    
  • Cough, dyspnea, increased sputum in complicated disease
    
  • Black sputum in coal workers
    
• Pulmonary hypertension, cor pulmonale
  
• PFTs – decreased diffusion capacity, obstructive, then restrictive defect
  
• Diagnosis by history of exposure, radiography/HRCT and/or lung biopsy
  
• Slight increased risk of lung cancer, scleroderma
  
• Prognosis
  
  • Simple, normal longevity
    
  • Complicated PMF, death from respiratory failure, pneumothorax, carcinoma, TB
    
  • Silicosisproteinosis: death within 2 to 3 years

Pendergrass EP. Some considerations concerning the roentgen diagnosis of pneujoconiosis and silicosis AJR 48:571-594, 1942
Remy-Jardin M, Degreef JM, Beuscart R, et al. Coal worker's pneumoconiosis: CT assessment in exposed workers and correlation with radiographic findings Radiology 177:363-371, 1990
Bergin CJ, Muller NL, Vedal S, et al. CT in silicosis: correlation with plain films and pulmonary function tests AJR 146:477-483, 1986