History
The clinical syndrome of farmer's lung, as with other types of hypersensitivity pneumonitis, is categorized as acute, subacute, or chronic.
Acute farmer's lung develops after large exposure to moldy hay or contaminated compost. Symptoms often spontaneously resolve within 12 hours to days if antigen exposure is eliminated or avoided. Acute farmer's lung manifests as new onset of fever, chills, nonproductive cough, chest tightness, dyspnea, headache, and malaise. If the inhalational exposure is large, patients may develop acute respiratory failure.
Subacute farmer's lung manifests as chronic cough, dyspnea, anorexia, and weight loss. Subacute disease is insidious in onset and may occur over weeks to months.
Chronic farmer's lung results from prolonged and continuous exposure to the antigen. Patients may have irreversible lung damage. Patients may experience severe dyspnea at rest or with exertion.
Physical Examination
In acute farmer's lung, physical findings are as follows:
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Fever
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Tachycardia
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Nonproductive cough
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Rales
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Rales that persist after fever subsides
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Wheezing (rare)
In subacute farmer's lung, physical findings are as follows:
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Normal examination findings between presentations
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Anorexia
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Weight loss
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Chronic nonproductive cough
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Generalized fatigue
In chronic farmer's lung, physical findings are as follows:
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Bibasilar rales
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Clubbing - More often observed in patients with chronic farmer's lung with long-standing hypoxemia and parenchymal damage
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Anorexia
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More severe dyspnea
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Weight loss
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Impaired exercise tolerance
