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Extrinsic allergic alveolitis
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Extrinsic allergic alveolitis

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Contributors: Mary Anne Morgan MD, Ryan R. Walsh MD, Joshua J. Jarvis MD, Alastair Moore MD
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Inflammation of lung parenchyma due to a hypersensitivity reaction to antigens. It manifests acutely with sudden-onset chest pain, cough, dyspnea, and fever following exposure to antigens. Headache, bibasilar crackles, inspiratory crackles, and malaise develop within 4-6 hours after exposure and may clear within 24 hours after removing the offending substance. The subacute form manifests gradually and less severely and may infrequently recur. A chronic form is characterized by an insidious onset of cough, fatigue, progressive dyspnea, and weight loss. Respiratory rate increases, and inspiratory crackles and respiratory distress often occur, with clubbing in half of patients.

Also known as hypersensitivity pneumonitis, farmer's lung, bird fancier's lung, and pigeon breeder's lung.

The first line of therapy is avoidance of the antigen causing the exaggerated immune response. Systemic corticosteroids or glucocorticoids may help in severe reactions. Longer exposure and greater intensity of exposure to bird antigens, development of digital clubbing, and older age all suggest a worsening of lung function and poorer prognosis. When identification of the offending antigen is made quickly and exposure has been of shorter duration, complete recovery has been reported.


J67.9 – Hypersensitivity pneumonitis due to unspecified organic dust

37471005 – Extrinsic allergic alveolitis

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Last Updated: 02/10/2016
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Extrinsic allergic alveolitis
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Extrinsic allergic alveolitis (Acute) : Chest pain, Chills, Cough, Fever, Headache, Developed rapidly , Malaise, Dyspnea, RR increased, Inspiratory crackles, Bibasilar crackles
Imaging Studies image of Extrinsic allergic alveolitis
Radiographs show hazy opacities throughout both lungs (straight black arrows). Small, poorly defined nodules are subtle (straight white arrows). There is relative sparing of the lung apices. Patient is a 63 year-old male with history of exposure to birds, presenting with low-grade fever and shortness of breath.
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