5.5 Sarcoidosis, Hypersensitivity Pneumonitis & Occupational Lung Disease
Key Takeaways
- Organic inhalations, inorganic inhalations, occupational asthma, high-altitude illness and carbon monoxide poisoning are enumerated under occupational and environmental lung disease.
- Lofgren syndrome of erythema nodosum, bilateral hilar adenopathy, fever and arthritis is a favorable sarcoidosis presentation often managed without corticosteroids.
- Hypersensitivity pneumonitis requires identification and removal of the inciting antigen, which is the single most important intervention.
- Silicosis markedly increases tuberculosis risk, so latent tuberculosis screening is mandatory in exposed workers.
- Eggshell calcification of hilar nodes suggests silicosis, and pleural plaques indicate asbestos exposure rather than asbestosis itself.
Last updated: August 2026
1. Sarcoidosis
Sarcoidosis is a multisystem inflammatory disorder characterized pathologically by the accumulation of noncaseating epithelioid granulomas in affected organs, most commonly the lungs and intrathoracic lymph nodes (>90% of cases).
Epidemiology & Pathophysiology
- Demographics: Peaks in young-to-middle-aged adults (20–45 years); 3- to 4-fold higher incidence and greater clinical severity in African Americans (particularly women) and individuals of Scandinavian descent.
- Immunopathology: CD4+ T-helper 1 (Th1) and Th17 cell hyperactivation driven by persistent antigen presentation, leading to interleukin-2 (IL-2), interferon-gamma (IFN-gamma), and TNF-alpha secretion. Bronchoalveolar lavage (BAL) characteristically reveals a marked lymphocytic alveolitis with an elevated CD4+/CD8+ ratio > 3.5:1.
- Calcium Metabolism Abnormalities: Activated alveolar macrophages within granulomas express 1-alpha-hydroxylase in an unregulated fashion, converting 25-hydroxyvitamin D into active 1,25-dihydroxyvitamin D (Calcitriol) independent of PTH. This results in hypercalciuria (common, ~30%) and hypercalcemia (~10%) with suppressed PTH and hypercalciuric nephrocalcinosis/nephrolithiasis.
Scadding Radiographic Staging (Chest X-Ray)
| Stage | Radiographic Findings | Typical Spontaneous Resolution Rate |
|---|---|---|
| Stage 0 | Normal chest radiograph (5–10% of presentations) | N/A |
| Stage I | Bilateral Hilar Lymphadenopathy (BHL) alone (+/- right paratracheal node enlargement) | 60% – 80% spontaneous remission |
| Stage II | Bilateral Hilar Lymphadenopathy + Parenchymal Infiltrates (reticulonodular upper/mid zone) | 50% – 60% spontaneous remission |
| Stage III | Parenchymal Infiltrates alone (diffuse fibrosis/opacities without hilar adenopathy) | 20% – 30% spontaneous remission |
| Stage IV | End-Stage Pulmonary Fibrosis (honeycombing, architectural distortion, upward hilar retraction) | 0% (Permanent, irreversible damage) |
Classical Clinical Syndromes & Extrapulmonary Screening
- Löfgren Syndrome: Classic acute benign presentation characterized by the clinical triad of:
- Bilateral hilar lymphadenopathy (BHL)
- Erythema nodosum (tender, erythematous subcutaneous pretibial nodules)
- Migratory polyarthritis or periarthritis (especially affecting bilateral ankles)
- Prognosis & Management: Excellent prognosis with >85% spontaneous remission within 1–2 years. Treated with NSAIDs alone for symptom relief. Systemic corticosteroids and invasive tissue biopsy are NOT required when the classic triad is present.
- Heerfordt Syndrome (Uveoparotid Fever): Rare manifestation presenting with parotid gland enlargement, anterior uveitis, low-grade fever, and cranial nerve VII (facial) palsy.
- Cardiac Sarcoidosis: Present in up to 25% of sarcoidosis autopsies. Manifests as complete atrioventricular (AV) heart block, ventricular arrhythmias (VT/VF), sudden cardiac death, or dilated cardiomyopathy. All patients with sarcoidosis require a baseline 12-lead ECG. If abnormal or palpitations/syncope occur, evaluate immediately with Cardiac MRI (late gadolinium enhancement) or 18F-FDG PET-CT.
- Ocular Sarcoidosis: Anterior/posterior uveitis, retinal vasculitis, or optic neuritis. Requires a mandatory baseline slit-lamp ophthalmologic examination in all patients.
- Neurosarcoidosis: Cranial neuropathies (CN VII palsy most common), aseptic meningitis, hypothalamic-pituitary dysfunction (diabetes insipidus), or seizures.
Indications for Systemic Corticosteroids
- Asymptomatic Stage I or stable mild Stage II pulmonary sarcoidosis does not require treatment (observation with serial PFTs every 3–6 months is standard).
- Mandatory Indications for Treatment:
- Progressive or symptomatic pulmonary disease (worsening dyspnea, declining FVC/DLCO)
- Cardiac sarcoidosis (AV block, ventricular arrhythmias, cardiomyopathy)
- Neurosarcoidosis
- Ocular sarcoidosis refractory to topical ophthalmic steroids
- Persistent hypercalcemia or nephrocalcinosis
- Disfiguring lupus pernio or symptomatic hepatosplenomegaly
- Therapeutic Regimen: Oral Prednisone 20–40 mg daily for 1–3 months, tapered over 6–12 months. Second-line steroid-sparing agents: Methotrexate (first-line add-on), Azathioprine, or Leflunomide. Refractory cases: Infliximab (anti-TNF-alpha).
2. Hypersensitivity Pneumonitis (Extrinsic Allergic Alveolitis)
Hypersensitivity Pneumonitis (HP) is an immune-mediated interstitial and bronchiolar lung disease triggered by repeated inhalation of environmental organic antigens (fungal spores, avian proteins, bacterial products) or low-molecular-weight chemicals in sensitized hosts.
Major Etiologic Antigens
- Farmer's Lung: Inhalation of thermophilic actinomycetes (Saccharopolyspora rectivirgula, Thermoactinomyces vulgaris) from moldy hay or compost.
- Bird Fancier's / Pigeon Breeder's Lung: Inhalation of avian serum proteins (droppings, bloom, feathers from pigeons, parakeets, chickens, down duvets/pillows).
- Hot Tub / Humidifier Lung: Inhalation of non-tuberculous mycobacteria (Mycobacterium avium complex) or molds (Aureobasidium, Cephalosporium) from contaminated aerosols.
- Chemical Worker's Lung: Inhalation of diisocyanates (polyurethane paints, foams) or trimellitic anhydride.
Diagnostic Hallmarks
- Clinical Phenotypes:
- Non-Fibrotic (Acute/Subacute) HP: Flu-like illness with fever, chills, non-productive cough, and dyspnea developing 4–8 hours after antigen re-exposure, resolving over 24–48 hours away from the exposure.
- Fibrotic (Chronic) HP: Insidious onset of progressive exertional dyspnea, fatigue, weight loss, and crackles due to continuous low-dose exposure.
- Bronchoalveolar Lavage (BAL): Marked lymphocytic alveolitis (>20–40% lymphocytes), often with a normal or low CD4+/CD8+ ratio (<1.0).
- HRCT Chest: Centrilobular ground-glass nodules, mosaic perfusion, and expiratory air-trapping. The pathognomonic "headcheese sign" (three-density sign) consists of juxtaposed areas of ground-glass opacity, normal lung attenuation, and lucent hypoperfused air-trapping on inspiratory and expiratory images.
- Management: Complete and strict avoidance of the offending environmental antigen is the cornerstone of treatment and the only intervention that halts disease progression. Oral corticosteroids (Prednisone 0.5–1 mg/kg/day tapered over 1–3 months) accelerate recovery in acute/subacute disease with physiological impairment.
3. Pneumoconioses: Occupational Mineral Dust Diseases
Pneumoconioses are non-neoplastic lung diseases caused by the inhalation, deposition, and tissue reaction to inorganic mineral dusts in industrial workplaces.
Summary of Major Pneumoconioses
| Condition | Industrial Exposure | Key Radiographic / Pathologic Findings | Major Complications & Board Pearls |
|---|---|---|---|
| Silicosis | Sandblasting, rock quarrying, tunneling, granite cutting, foundry work, ceramics, glass manufacturing. | - Chest X-Ray: Multiple small, discrete rounded nodular opacities (1–10 mm) predominantly in the upper lung lobes.<br/>- Classic "Eggshell Calcification" of hilar and mediastinal lymph nodes (thin calcified rim).<br/>- Histology: Concentric, whorled hyalinized collagenous silicotic nodules with weakly birefringent silica crystals under polarized light. | - Silicotuberculosis: Silica impairs alveolar macrophage phagolysosomal killing of Mycobacterium tuberculosis.<br/>- Mandatory annual TB screening with TST (PPD) or IGRA.<br/>- A TST induration >= 5 mm is considered POSITIVE in silicosis.<br/>- Increased risk of lung cancer and systemic sclerosis (Erasmus syndrome). |
| Asbestosis & Asbestos Pleural Disease | Shipbuilding, naval shipyards, pipefitting, construction demolition, boiler making, insulation, automotive brake repair (latency 15–40+ years). | - Benign Pleural Plaques: Well-circumscribed fibrocalcific plaques on the parietal pleura and dome of the diaphragm (sparing costophrenic angles). Most common manifestation; indicates exposure only (not premalignant).<br/>- Asbestosis (Parenchymal Fibrosis): Bibasilar reticular interstitial fibrosis, honeycombing, and thickened pleura.<br/>- Histology: Asbestos (ferruginous) bodies (golden-brown beaded dumbbell-shaped fibers coated with hemosiderin-protein). | - Bronchogenic Carcinoma: Most common malignancy in asbestos workers; risk is multiplicatively synergistic with cigarette smoking (up to 50–90x risk).<br/>- Malignant Mesothelioma: Aggressive tumor of the parietal pleura presenting with pleuritic pain, dyspnea, and hemorrhagic pleural effusion with nodular pleural rind. NOT associated with cigarette smoking; associated almost exclusively with asbestos exposure. |
| Coal Workers' Pneumoconiosis (CWP) | Underground coal mining (anthracite coal miners). | - Simple CWP: Small rounded opacities (coal macules / nodules) in upper lung zones.<br/>- Complicated CWP: Progressive Massive Fibrosis (PMF) with large confluent fibrotic masses (>1 cm) causing cavitation and severe restrictive/obstructive impairment. | - Caplan Syndrome: Combination of pneumoconiosis (CWP or silicosis) with Rheumatoid Arthritis, presenting as multiple well-defined peripheral pulmonary rheumatoid nodules (1–5 cm) that may cavitate. |
Test Your Knowledge
A 32-year-old African American woman presents to the clinic with a 2-week history of tender, painful red nodules on her anterior shins, low-grade fevers, and severe pain and swelling in both ankles that limits her ambulation. She has no chronic medical conditions and takes no medications. Physical examination reveals warm, erythematous, exquisitely tender subcutaneous nodules along both pretibial surfaces and bilateral periarticular ankle warmth, swelling, and tenderness. Cardiopulmonary examination is normal. A chest radiograph demonstrates marked, symmetric bilateral hilar and right paratracheal lymphadenopathy with clear lung parenchyma. Complete blood count and serum creatinine are normal. Which of the following is the most appropriate management plan?
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D
Test Your Knowledge
A 54-year-old man who worked for 22 years as a sandblaster and rock quarry drill operator presents for an employment physical. He is asymptomatic with no cough, fever, weight loss, or dyspnea on exertion. Physical examination is unremarkable. A screening chest radiograph reveals multiple 2- to 5-mm rounded nodular opacities in both upper lung fields, accompanied by prominent peripheral rim-like 'eggshell calcification' of the hilar and mediastinal lymph nodes. Which of the following is the most appropriate management for this patient?
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B
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D