Background: Acute eosinophilic pneumonia (AEP) is characterized by a febrile illness, diffuse pulmonary infiltrates, and pulmonary eosinophilia. The etiology of AEP remains unknown, but several studies have proposed a relationship between cigarette smoking and AEP. However, most studies showing this possibility are single-case reports, and cigarette smoke has not been fully validated as a causative agent of AEP in a large series of patients. The present study was conducted to clarify the etiologic role of cigarette smoking in AEP, with special reference to alterations in smoking habits.
Methods: We took a detailed history of smoking habits before AEP onset in 33 patients with AEP, and performed a cigarette smoke provocation test.
Results: Of our AEP patients, all but one (97%) were current smokers. Interestingly, 21 of these were new-onset smokers, and 2 had restarted smoking after a 1- to 2-year cessation of smoking. The duration between starting smoking and AEP onset was within 1 month (0.67 ± 0.53 months). Additionally, six of the remaining smokers had increased the quantity of cigarettes smoked daily, fourfold to fivefold, mostly within the month before AEP onset (0.81 ± 0.58 months). Only three smokers had not changed their smoking habits before AEP onset. Cigarette smoke provocation tests revealed positive results in all nine patients tested.
Conclusion: These data suggest that recent alterations in smoking habits, not only beginning to smoke, but also restarting to smoke and increasing daily smoking doses, are associated with the development of AEP.