ABSTRACT
Agents causing hypersensitivity pneumonitis (HP) include numerous fungi and microorganisms, animal and plant products as well as chemicals. Farmer's lung due to moldy hay is the most widely known occupational HP. Symptoms, mainly shortness of breath and cough accompanied by chills and fever, occur according to various time frames, from acute to chronic. The syndrome is characterized by lymphocytic alveolitis that manifests by an interstitial lung disease associated with a restrictive and gas exchange functional defect as well as the production of specific IgG antibodies. Besides systemic symptoms (chills, fever, fatigue, etc.), dyspnea at rest and on exercise and coughing are the most frequent symptoms in subjects with HP. Clinical, radiological, functional, and laboratory tests are proposed in the investigation of subjects with potential HP. Manifestations can be acute or chronic. The histopathological triad of HP in its acute form includes bronchiocentric lymphohistiocytic interstitial pneumonia with bronchiolitis and typical small poorly shaped nonnecrotizing granulomas. Occupational HP should be considered if a worker presents with recurrent episodes of fever and dyspnea, with a time schedule related to exposure at work, and in the investigation of interstitial lung disease of unknown etiology. In the case of occupational HP as for occupational asthma (OA), once the diagnosis is confirmed, that is the disease is caused by work even if the responsible agent has not been identified, removal from exposure is the most relevant advice.
