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For further information, see CMDT Part 9-33: Occupational Pulmonary Diseases

KEY FEATURES

Essentials of Diagnosis

  • A link between symptoms and antigen exposure may be obtained from work or environmental history

  • Exposure to inhaled microbial, avian, and animal antigens, and less commonly to an inorganic agent

  • Presentation can be acute or subacute illness

General Considerations

  • A nonatopic, nonasthmatic inflammatory pulmonary disease (also called extrinsic allergic alveolitis)

  • Manifested mainly as occupational disease where exposure to an inhaled organic antigen leads to an acute illness

  • Causes

    • See Table 9–21

    • Farmer's lung (moldy hay)

    • "Humidifier" lung (contaminated humidifier, heating, or air conditioning)

    • Bird fancier's lung ("pigeon breeder's disease")

    • Bagassosis (moldy sugar cane fiber)

    • Sequoiosis (moldy redwood sawdust)

    • Maple bark stripper's disease

    • Mushroom picker's disease (moldy compost)

    • Suberosis (moldy cork dust)

    • Detergent worker's lung (enzyme additives)

Table 9–21.Selected causes of hypersensitivity pneumonitis.

CLINICAL FINDINGS

Symptoms and Signs

  • Acute illness 4–8 hours after exposure characterized by

    • Malaise

    • Chills

    • Low-grade fever

    • Cough

    • Dyspnea

    • Nausea

  • Bibasilar crackles, tachypnea, tachycardia, and (occasionally) cyanosis are found

  • Subacute and chronic illness (15% of cases)

    • Insidious onset of chronic cough and progressive dyspnea

    • With continued exposure, slowly progressive dyspnea

Differential Diagnosis

  • Sarcoidosis

  • Asthma

  • Atypical pneumonia

  • Collagen vascular disease, eg, systemic lupus erythematosus

  • Idiopathic pulmonary fibrosis

  • Lymphoma

DIAGNOSIS

Laboratory Tests

  • Pulmonary function tests show a restrictive pattern with reduced diffusing capacity

  • White blood count shows leukocytosis with a left shift

  • Arterial blood gases show hypoxemia

  • Hypersensitivity pneumonitis antibody panels are available; positive results while supportive do not establish a definitive diagnosis

Imaging Studies

  • Chest radiograph classically shows small nodular densities sparing the apices and bases

  • Pulmonary fibrosis may be found with repeated exposure to the offending agent

  • High-resolution CT findings of non-fibrotic disease include upper-/mid-lung ground glass or nodular opacities and signs of air trapping

Diagnostic Procedures

  • Bronchoscopy with bronchoalveolar lavage

  • Surgical lung biopsy may be necessary

TREATMENT

Medications

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