Silicosis

Pathophysiology

1) pneumoconiosis owing to chronic inhalation of crystalline silicon dioxide 2) can result in pulmonary fibrosis from chronic injury to lung tissue

Signs and Symptoms

1) nonproductive cough 2) in advanced disease with pulmonary fibrosis, dyspnea and tachypnea occur

Characteristic Test Findings

Radiology – 1) chest radiograph shows “eggshell” calcifications in hilar lymph nodes and honeycomb lung PFTs – 2) both restrictive and obstructive impairment occurs

Histology/Gross Pathology

1) macrophages phagocytose silica particles 2) results in nodule formation in lung parenchyma (areas of fibrosis entrapping silica particles) 3) especially affects upper lung lobes

Associated Conditions

1) increased incidence of tuberculosis 2) Caplan’s syndrome (fibrosis and rheumatoid disease)

Biochemistry

macrophages are killed when they engulf silica, with the resultant destruction of phagolysosomes and release of free radicals, proteases, and Il-1

Inheritance/Epidemiology

occurs in sandblasters, miners, and people who work in quarries

Treatment

removal from offending environment

Tips for USMLE

1) no increased risk of cancer 2) fibrosis may be progressive even though exposure stops