Occupational Lung Diseases

Intro & Pathogenesis - Workplace Woes

• Occupational Lung Diseases (OLDs): Lung conditions from inhaling harmful agents (dusts, chemicals, fumes) at work.
• Key Pathogenesis Factors:
  • Particle Size: 1-5 µm = greatest risk (reach alveoli).
  • Deposition: Via impaction, sedimentation, diffusion based on size.
  • Clearance: Mucociliary escalator & alveolar macrophages. Overwhelm or dysfunction leads to accumulation & injury.
  • Host Factors: Smoking, genetics, immune status modify risk.
  • Common Pathway: Persistent inflammation → cytokine release → fibrosis.

⭐ Particles 1-5 µm in diameter are most fibrogenic as they deposit in terminal airways and alveoli, triggering macrophage response and subsequent inflammation/fibrosis if clearance fails or exposure is chronic and heavy.

Silicosis & CWP - Deadly Dusts

Silicosis and Coal Worker's Pneumoconiosis (CWP) are fibrotic lung diseases from inhaling inorganic dusts (particle size <5µm), primarily affecting upper lobes.

Asbestosis & Mesothelioma - Fibers of Fate

• Asbestos Fibers: Amphibole (straight, more pathogenic, e.g., crocidolite) vs. Serpentine (curly, e.g., chrysotile).
• Asbestosis:
  • Diffuse interstitial fibrosis, predominantly in lower lobes.
  • Latency: 10-20 yrs.
  • Asbestos bodies (ferruginous bodies): Golden-brown, beaded, iron-coated fibers.
    • 
  • Leads to restrictive lung disease, "honeycomb lung" in advanced cases.
• Pleural Plaques:
  • Most common manifestation of asbestos exposure.
  • Well-demarcated, often calcified, dense collagen deposits on parietal pleura (especially posterolateral surfaces, diaphragm). Usually asymptomatic.
    • 
• Mesothelioma:
  • Malignancy of pleura (80%) or peritoneum; strong link to asbestos (especially amphiboles).
  • Latency: Long, 25-45 yrs.
  • Symptoms: Chest pain, dyspnea, recurrent, often hemorrhagic, pleural effusions.

  • Markers: Calretinin+, WT-1+, CK5/6+.

  ⭐ Smoking is NOT a risk factor for mesothelioma, unlike for asbestos-related lung cancer.

• Lung Cancer (Bronchogenic Carcinoma):
  • Most common cancer in asbestos-exposed individuals.
  • 📌 Asbestos exposure + Tobacco smoking = Synergistic (multiplicative) ↑↑ risk for lung cancer.

Organic Dusts & Asthma - Reactive Airways

• Hypersensitivity Pneumonitis (HP): Immune (Type III/IV) reaction to inhaled organic dusts.
  • Acute: Fever, cough, dyspnea 4-6 hrs post-exposure.
  • Chronic: Fibrosis, non-caseating granulomas.
  • 
• Types of HP:

  Antigen	Source	Disease Name
  Thermophilic actinomycetes	Moldy hay, sugarcane	Farmer's Lung, Bagassosis
  Avian proteins	Bird droppings/feathers	Bird Fancier's Lung
  Aspergillus spp.	Contaminated barley	Malt Worker's Lung

• Occupational Asthma: Airway hyperresponsiveness from workplace agents.
  • Sensitizer-induced (latency) vs. Irritant-induced (RADS, no latency).
  • Symptoms improve away from work.
• Byssinosis: "Monday Fever" from cotton/flax/hemp dust (endotoxin). Chest tightness on 1st workday.
• Flowchart: Occupational Asthma Classification

⭐ Farmer's Lung (Thermophilic actinomycetes in moldy hay) is the most common type of Hypersensitivity Pneumonitis.

High‑Yield Points - ⚡ Biggest Takeaways

• Silicosis: Upper lobes, eggshell calcification, ↑ TB risk.
• CWP: Upper lobes, coal macules; PMF if complicated.
• Asbestosis: Lower lobes, pleural plaques (commonest), ferruginous bodies; ↑ mesothelioma & bronchogenic Ca risk.
• Berylliosis: Granulomatous disease (mimics sarcoidosis), aerospace; BeLPT for diagnosis.
• Byssinosis: Cotton dust exposure, "Monday fever" (chest tightness).
• Caplan Syndrome: Pneumoconiosis + Rheumatoid Arthritis + necrobiotic nodules.
• Hypersensitivity Pneumonitis: e.g., Farmer's Lung (moldy hay), immune-mediated.