A 52–year–old previously healthy woman was admitted to our institution with a chief complaint of dyspnea, dry cough, and fever worsening over 4 days. Her past medical history was positive for lung adenocarcinoma for which she underwent right upper lobe lobectomy in 1992. Three weeks prior to admission she began smoking 4–5 cigarettes per day. She had experienced several months of extensive daily dust exposure from remodeling at her workplace. Physical examination revealed an oxygen saturation of 88% on room air and bibasilar crackles. Laboratory data showed WBC 12.7 with 7.3% eosinophils, and arterial blood gas 7.38/47/64 on 3.5 L/min oxygen. Chest radiograph(CXR) revealed diffuse increased interstitial markings. Bronchoalveolar lavage(BAL) of the right middle lobe revealed 51% eosinophils. Transbronchial lung biopsy revealed focal interstitial fibrosis and inflammation, without evidence of infection. On hospital day 4, she was weaned to room air, started on 40 mg prednisone daily with a brisk response and was discharged.
Acute eosinophilic pneumonia (AEP) is a rare cause of acute respiratory failure. It is an acute febrile illness with cough, chest pain, and dyspnea for <7 days, diffuse pulmonary infiltrates on CXR, hypoxemia, no history of asthma or atopic disease, no evidence of infection, and >25% eosinophils on BAL. With fewer than 100 cases reported, little is known about the etiology of AEP. It is presumed to be an acute hypersensitivity reaction to an inhaled allergen. Cigarette smoking and fine particle dust exposure have been proposed as a causative factor of AEP. A recent report of 18 cases of AEP in the Middle East confirmed an association of the disease with both chronic dust exposure and new onset smoking. These authors proposed that small dust particles irritate alveoli, stimulating eosinophils which are exacerbated by the onset of smoking; alternatively, cigarette smoke may prime the lung such that dust triggers an inflammatory cascade resulting in AEP. Our case of AEP supports the potential link between dust exposure and new onset cigarette smoking. Our case also demonstrates the importance of a thorough patient history and the diagnostic importance of BAL.
Consider AEP in a patient with acute respiratory failure and diffuse infiltrates on CXR of unknown cause. New onset tobacco smoking is a risk factor for AEP. Our case supports a link between dust exposure and new onset smoking in AEP.