Sarcoidosis - Pulmonary

Definition

Pulmonary sarcoidosis is a systemic granulomatous disease of unknown etiology, predominantly affecting the lungs and intrathoracic lymph nodes, characterized by non-caseating granulomas and variable clinical course.

Epidemiology

• Incidence highest in adults aged 20–40 years
• More common in women than men
• Higher prevalence in African-American and Northern European populations
• Estimated prevalence: 10–40 per 100,000 in general population
• Often detected incidentally on chest imaging

Etiology

• Unknown; likely immune-mediated response to environmental or infectious antigens
• Genetic susceptibility (HLA genotypes associated)
• Possible environmental triggers: inorganic dust, beryllium, mold, microbes
• Immunologic dysregulation with exaggerated T-helper cell response
• No single causative pathogen identified
• Familial clustering in some cases

Pathophysiology

• Activation of alveolar macrophages and CD4+ T-helper cells
• Formation of non-caseating granulomas in lung parenchyma and lymph nodes
• Cytokine release (TNF-α, IL-2, IFN-γ) promotes granuloma formation
• Fibrotic remodeling may occur in chronic disease
• Airway obstruction and restrictive lung defect can develop
• Vascular involvement may lead to pulmonary hypertension
• Systemic granulomatous inflammation can affect multiple organs