Acute Eosinophilic Pneumonia Among US Military Personnel Deployed in or Near Iraq

CONTEXT: Acute eosinophilic pneumonia (AEP) is a rare disease of unknown etiology characterized by respiratory failure, radiographic infiltrates, and eosinophilic infiltration of the lung. OBJECTIVES: To describe a case series of AEP, illustrate the clinical features of this syndrome, and report the results of an epidemiologic investigation. DESIGN, SETTING, AND PARTICIPANTS: Epidemiologic investigation of cases of AEP identified both retrospectively and prospectively from March 2003 through March 2004 among US military personnel deployed in or near Iraq. Survivors were offered a follow-up evaluation. MAIN OUTCOME MEASURE: Morbidity and mortality related to AEP. RESULTS: There were 18 cases of AEP identified among 183,000 military personnel deployed in or near Iraq during the study period, yielding an AEP incidence of 9.1 per 100,000 person-years (95% confidence interval, 4.3-13.3). The majority of patients (89%) were men and the median age was 22 (range, 19-47) years. All patients used tobacco, with 78% recently beginning to smoke. All but 1 reported significant exposure to fine airborne sand or dust. Known causes of pulmonary eosinophilia (eg, drug exposures or parasitic disease) were not identified. Epidemiologic investigation revealed no evidence of a common source exposure, temporal or geographic clustering, person-to-person transmission, or an association with recent vaccination. Six patients underwent bronchoalveolar lavage (median eosinophilia of 40.5%). All patients developed peripheral eosinophilia (range, 8%-42%). Mechanical ventilation was required in 67% for a median of 7 (range, 2-16) days. Two soldiers died; the remainder responded to corticosteroids and/or supportive care. Twelve individuals were reevaluated a median of 3 months after diagnosis. At that point, 3 patients reported mild dyspnea and 1 reported wheezing. All patients had finished treatment and had either normal or nearly normal spirometry results. None had recurrent eosinophilia. CONCLUSIONS: AEP occurred at an increased rate among this deployed military population and resulted in 2 deaths. Failure to consider AEP in the differential diagnosis of respiratory failure in military personnel can result in missing this syndrome and possibly death. The etiology of AEP remains unclear, but the association with new-onset smoking suggests a possible link.