Ultrastructural and immunohistochemical evidence for release of eosinophilic granules in vivo: cytotoxic potential in chronic eosinophilic pneumonia.

We studied a patient with relapsing idiopathic chronic eosinophilic pneumonia. Each one of four attacks observed during a 4-year period was characterized by dyspnea, wheezing, peripheral blood eosinophilia, elevated serum IgE levels, and pulmonary infiltrates. Glucocorticoid therapy caused prompt resolution of symptoms and disappearance of blood eosinophilia and pulmonary shadowing. Electron microscopy and tissue immunofluorescence studies for major basic protein documented extensive eosinophil degranulation and the presence of free granules within the pulmonary microvasculature. In addition, exfoliation of the alveolar lining cell was observed in association with a clustering of free intact and disintegrating extracellular eosinophil granules against a denuded basement membrane. These findings suggest a cytotoxic potential of the eosinophil at the level of the pulmonary parenchyma in a case of idiopathic chronic eosinophilic pneumonia.