Nuclear hypersegmentation precedes the increase in blood eosinophils in acute eosinophilic pneumonia.

In this case of acute eosinophilic pneumonia (AEP), eosinophils with hypersegmented nuclei emerged in the blood before the increase of eosinophil count. An 18-year-old woman complaining of fever, cough and dyspnea was admitted because of diffuse ground-glass opacities in her chest roentgenogram. On admission, her blood cell count revealed a marked increase of neutrophils. Although the number of eosinophils was normal, some of them contained three- or four-lobed nuclei. She was diagnosed to have AEP through bronchoalveolar lavage and transbronchial lung biopsy. The combination with acute clinical course, pulmonary infiltration and the presence of hypersegmented eosinophils in blood may imply the diagnosis of AEP.