Pneumoconiosis is caused by the accumulation of inhaled particulates. Pneumoconiosis may be classified as fibrotic (involving focal nodular or diffuse fibrosis) or nonfibrotic (involving particle laden macrophages, with minimal or no fibrosis).

Types of Pneumoconiosis

• Fibrotic pneumoconiosis
  
  
  
  • Silicosis
    
  • Coal worker pneumoconiosis
    
  • Asbestosis
    
  • Berylliosis
    
  • Talcosis
  
  
• Nonfibrotic pneumoconiosis
  
  
  
  • Siderosis (from iron oxide)
    
  • Stannosis (from tin oxide)
    
  • Barytosis (from barium sulfate)

Silicosis, coal worker pneumoconiosis, and asbestosis are the three most common types of pneumoconiosis, whereas berylliosis, siderosis, stannosis, and barytosis are relatively uncommon.

Silicosis

Silicosis is caused by the inhalation of fine particles of crystalline silicon dioxide (silica). Quartz is the most common form of crystalline silica. The disease occurs in two clinical forms: acute silicosis, which manifests as alveolar silicoproteinosis, and classic silicosis, which manifests as chronic interstitial reticular nodular disease.

On computed tomography (CT), two main patterns are recognized: simple and complicated.

The simple form is characterized by multiple nodules, which are well defined and uniform in shape, and attenuation is distributed throughout both lungs. However, the nodules tend to be predominantly located in the upper lobes and posterior portions of the lungs. The nodules in simple silicosis tend to be more sharply defined than those in coal worker’s pneumoconiosis are, but are otherwise indistinguishable from the latter on thin-section CT. The nodules are distributed in centrilobular, periseptal, and subpleural regions and have a perilymphatic distribution. Hilar and mediastinal lymph node enlargement may precede the appearance of parenchymal nodular lesions. The so-called eggshell calcification pattern is highly suggestive of silicosis.

Complicated silicosis or progressive massive fibrosis is characterized by large conglomerate opacities. Carcinoma and tuberculosis are potential serious complications of silicosis.