Occupational Lung Disease - Detailed Clinical Note (15 Marks - BPT MGR University)

Definition

• Harrison's Principles of Internal Medicine, 22e, p.2278: "Occupational and environmental lung diseases are difficult to distinguish from those of nonenvironmental origin."

Classification (NIOSH 5 Major Groups)

PART A: PNEUMOCONIOSES

1. Silicosis

• Silica particles (0.5-5 µm) deposit in alveoli
• Phagocytosis by alveolar macrophages triggers inflammasome activation
• Release of fibrogenic cytokines (IL-1, TNF-alpha) causes fibrosis
• Characteristic lesion: silicotic nodule - concentric whorled collagen surrounding a central dust core
• May progress to Progressive Massive Fibrosis (PMF) - nodules >1 cm coalescing in upper lobes

• Simple silicosis: small nodules (<1 cm), often asymptomatic
• Accelerated silicosis: develops within 10 years of intense exposure
• Acute silicosis: rapid alveolar filling pattern (silicoproteinosis) after massive short-term exposure
• PMF: large confluent masses, upper lobes, severe disability

• Insidious onset dyspnea on exertion progressing to rest
• Dry cough
• Reduced exercise tolerance
• On examination: bilateral fine basal crackles, later harsh breath sounds
• Advanced cases: cor pulmonale, cyanosis, clubbing

• Tuberculosis (silicotuberculosis) - significantly increased susceptibility
• Lung cancer (increased risk)
• COPD
• Scleroderma
• Caplan syndrome (pneumoconiosis + rheumatoid arthritis)

• Chest X-ray: bilateral upper-lobe nodules ("eggshell calcification" of hilar nodes is classic)
• HRCT: centrilobular and subpleural nodules, PMF masses
• PFTs: restrictive pattern (reduced TLC, FVC); later mixed restrictive-obstructive
• Reduced DLCO (diffusing capacity)

2. Coal Worker's Pneumoconiosis (CWP) / "Black Lung Disease"

• Coal dust deposited in alveoli and respiratory bronchioles
• Macrophage phagocytosis → inflammatory cytokines → "coal macule" formation (carbon-laden macrophages around respiratory bronchioles)
• Progressive: macule → nodule → PMF

• Simple CWP: often asymptomatic; cough with black sputum (melanoptysis)
• PMF: severe dyspnea, productive cough, respiratory failure
• Physical exam: reduced breath sounds, crackles
• May develop cor pulmonale

• Chest X-ray: small round opacities in upper and mid zones
• HRCT: centrilobular nodules (well-defined)
• PFTs: restrictive or mixed pattern

3. Asbestosis

• Long asbestos fibers deposit in lower lobes
• Macrophage engulfment → incomplete phagocytosis → persistent inflammation
• "Asbestos bodies" (ferruginous bodies) - fibers coated with iron-protein complex
• Interstitial fibrosis (usual interstitial pneumonia pattern) predominantly in lower lobes

• Progressive dyspnea on exertion
• Dry, non-productive cough
• Digital clubbing (distinctive feature, unlike other pneumoconioses)
• Bilateral fine basal inspiratory crackles (Velcro crackles)
• Cyanosis in advanced disease
• Signs of cor pulmonale in late stage

• Chest X-ray: bilateral irregular opacities predominantly in lower zones; pleural plaques; "shaggy heart" border
• HRCT (best diagnostic tool): subpleural reticulation, honeycombing, ground-glass opacity, pleural plaques
• PFTs: restrictive pattern - reduced FVC, TLC; reduced DLCO
• BAL: asbestos bodies (ferruginous bodies) confirm exposure
• Serum mesothelin/osteopontin: markers for mesothelioma

• Cigarette smoking + asbestos = synergistic 50-90x increased risk of lung cancer
• Family members of asbestos workers also at risk (para-occupational exposure)

PART B: WORK-RELATED ASTHMA (Occupational Asthma)

1. Sensitizer-induced OA (after latency period): IgE-mediated (high molecular weight agents - flour, latex) or non-IgE cell-mediated (low molecular weight - isocyanates, wood dust)
2. Irritant-induced OA (no latency): RADS (Reactive Airways Dysfunction Syndrome) after single high-level exposure to irritant gas

• Wheezing, chest tightness, cough, dyspnea
• Characteristically worse on workdays, improves on weekends/holidays
• Two key screening questions: "Do your symptoms improve away from work?" and "Have you ever been exposed to fumes, dusts or gases?"

• Serial peak expiratory flow (PEF) monitoring: at work vs. off work
• Spirometry: FEV1/FVC <0.7, reversibility with bronchodilator
• Specific bronchoprovocation challenge (gold standard)
• Skin prick test / specific IgE (for sensitizer OA)

PART C: HYPERSENSITIVITY PNEUMONITIS (Extrinsic Allergic Alveolitis)

• Repeated inhalation → antigen-antibody complexes (IgG precipitins) in alveolar walls → complement activation (Type III)
• Activated CD4+ T cells → granuloma formation (Type IV)
• Combined response → interstitial inflammation → fibrosis if untreated

• Serum precipitins (IgG antibodies) - confirms exposure, not disease
• HRCT: ground-glass opacity, centrilobular nodules, mosaic attenuation; fibrosis in chronic form
• BAL: lymphocytosis (CD8+ predominance in acute)
• PFTs: restrictive pattern with reduced DLCO
• Lung biopsy: poorly formed non-caseating granulomas in bronchiolar walls (pathognomonic)

PART D: BYSSINOSIS

• Grade 0: No symptoms
• Grade 1/2: Chest tightness on Monday only
• Grade 1: Chest tightness every Monday
• Grade 2: Chest tightness every day of work week
• Grade 3: Permanent disability with dyspnea

PART E: ACUTE IRRITANT/TOXIC INHALATION

• Water-soluble agents (ammonia, sulfur dioxide, chlorine): irritate upper airways and proximal bronchi; laryngospasm, bronchospasm immediately
• Low-solubility agents (nitrogen dioxide, phosgene, ozone): penetrate to bronchioles/alveoli; may cause delayed acute chemical pneumonitis with pulmonary edema (6-24 hours after exposure)
• Metal fume fever: inhalation of zinc oxide fumes (galvanizers, welders) - fever, chills, myalgia starting 4-8 hours after exposure; resolves within 24 hours; "Monday disease"

General Principles of Diagnosis

1. Detailed occupational history (most important) - ask about all past and present jobs, specific exposures, temporal relationship of symptoms to work
2. Two key screening questions:
   • "Have you ever been exposed to fumes, gases, or dust?"
   • "Do symptoms improve away from work (weekends/holidays)?"
3. Chest X-ray and HRCT
4. Pulmonary function tests (PFTs)
5. Specific tests based on disease type

Particle Size and Site of Deposition:

• >10-15 µm: Deposited in nose/throat (filtered out)
• 2.5-10 µm (coarse mode): Deposited in tracheobronchial tree (silica, aluminum, iron)
• <2.5 µm (fine mode): Deposit in lower airways and alveoli (most dangerous)
• <0.1 µm (ultrafine/nanoparticles): May pass to circulation and extrapulmonary sites

Management (General Principles)

1. Remove patient from exposure - single most important intervention
2. No smoking - smoking dramatically worsens all pneumoconioses; 50-90x cancer risk with asbestos
3. Bronchodilators - for airflow obstruction
4. Corticosteroids - for hypersensitivity pneumonitis and acute inflammatory phases (pneumoconioses respond poorly)
5. Supplemental O2 - for hypoxemia
6. Pulmonary rehabilitation - breathing exercises, exercise training, energy conservation
7. Treat complications - TB prophylaxis/treatment in silicosis, right heart failure management
8. Lung transplantation - in end-stage disease

Physiotherapy Role (BPT Specific):

• Breathing exercises (diaphragmatic breathing, pursed lip breathing)
• Airway clearance techniques (ACBT, postural drainage)
• Exercise training programs
• Energy conservation strategies
• Patient education on exposure prevention and respiratory protective equipment
• Monitoring using peak flow meters
• Pulmonary rehabilitation

Prevention

• Engineering controls: dust suppression, adequate ventilation, enclosed operations
• Personal protective equipment: respirators (N95/P100 masks), but imperfect - worksite air quality improvement is priority
• Biological monitoring: regular chest X-rays, PFTs for exposed workers
• Legislation: OSHA/TLV standards for dust exposure
• Substitution of hazardous materials where possible
• Health surveillance programs

Summary Table: Key Differentiating Features