1. Definition
Silicosis is a restrictive chronic lung disease (pneumoconioses) caused by inhalation of silica dust, leading to inflammation, fibrosis (scarring), and reduced lung function.
2. Pathophysiology
The progression of silicosis is driven by the body’s inflammatory and fibrotic response to inhaled silica particles:
- Inhalation: Crystalline silica particles are inhaled into the lungs
- Particle Deposition: Fine particles (<3 µm) are deposited in the alveoli, the tiny air sacs in the lungs
- Immune Response:
- The highly electronegative surface of the silica particle triggers a strong immune reaction in macrophages
- Macrophages phagocytize the silica particles but can not degrade them
- This leads to the release of inflammatory signals (cytokines) like TNF-α and interleukins
- Fibrosis:
- Continuous inflammation causes fibroblasts to produce collagen, resulting in scarring and formation of nodules
- Over time, these nodules coalesce, leading to progressive massive fibrosis (PMF) in advanced cases
- Lung Restriction:
- The fibrosis makes the lungs less elastic, reducing their ability to expand and contract
3. Symptoms
- Chronic cough (dry or productive)
- Shortness of breath, initially on exertion, later at rest
- Fatigue and chest discomfort
4. Types
- Chronic Silicosis: Develops after decades of low-to-moderate exposure. Nodules form primarily in the upper lobes
- Accelerated Silicosis: Develops within 5–10 years of intense exposure
- Acute Silicosis: Rapid onset (months to a few years) with severe inflammation and respiratory failure
5. Complications
- Increased risk of tuberculosis (silicotuberculosis)
- Co-occurring chronic obstructive pulmonary disease (COPD)
- Development of autoimmune diseases like rheumatoid arthritis
6. Treatment
Silicosis has no definitive cure. Management focuses on symptom control and prevention of complications:
- Medical Treatment:
- Symptom relief with bronchodilators or corticosteroids.
- Treatment of infections, especially tuberculosis.
- Oxygen Therapy: For patients with advanced disease and hypoxemia.
- Advanced Interventions:
- Lung transplantation in end-stage cases.
- Supportive Measures:
- Pulmonary rehabilitation.
- Vaccination against influenza and pneumococcal infections.