Chronic eosinophilic pneumonia. Ultrastructural evidence of marked immunoglobulin production plus macrophagic ingestion of eosinophils and eosinophilic lysosomes leading to intracytoplasmic Charcot-Leyden crystals.

A 60-year-old man was diagnosed as having chronic eosinophilic pneumonia by clinical presentation and open lung biopsy. Electron microscopic study of the tissue from biopsy revealed evidence of marked production of immunoglobulin, which may be part of the chemotactic process which attracted large numbers of eosinophils into the area. Also, there were macrophages which were phagocytosing degenerating eosinophils and eosinophilic lysosomes. Charcot-Leyden crystals were noted in the cytoplasm of many macrophages. The relationship of the production of immunoglobulin to the eosinophilia and the mechanism of intramacrophagic formation of Charcot-Leyden crystals is discussed.