## Silicosis: Occupational Pneumoconiosis **Key Point:** Silicosis is a chronic occupational lung disease caused by inhalation of crystalline silicon dioxide (SiO~2~) dust, resulting in progressive pulmonary fibrosis. ### Definition and Pathophysiology Silicosis occurs when workers inhale respirable crystalline silica particles (< 5 μm diameter) that deposit in the alveoli and trigger a fibrotic response. The silica particles are phagocytosed by macrophages, leading to inflammation and collagen deposition. ### High-Risk Occupations - Stone cutters and masons - Sandblasters - Quarry workers - Foundry workers - Miners (coal, metal, stone) - Ceramic and pottery workers ### Classification of Silicosis | Type | Latency | Progression | Radiological Features | |------|---------|-------------|----------------------| | Acute | Weeks to months | Rapid, fulminant | Alveolar opacities | | Accelerated | 5–10 years | Progressive | Nodular opacities | | Chronic | > 10 years | Slow | Small rounded opacities (ILO 1/0 to 3/3) | **Mnemonic:** **SILICA** — **S**mall nodular opacities, **I**nflammation and fibrosis, **L**ung function decline, **I**nhalation of crystalline silica, **C**hronic progressive disease, **A**pex and upper lobe predominance. **Clinical Pearl:** Silicosis has a characteristic "eggshell" calcification of hilar lymph nodes on chest X-ray, a pathognomonic finding in advanced disease. **High-Yield:** Silicosis is a notifiable occupational disease in India and workers are entitled to compensation under the Workmen's Compensation Act. ### Complications - Pulmonary tuberculosis (silica impairs macrophage function) - Chronic obstructive pulmonary disease (COPD) - Cor pulmonale - Lung cancer (silica is a Class 1 carcinogen)
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