Unusual inclusions in mature polymorphonuclear neutrophils of cyclic neutropenia.

The bone marrow of an 11-year-old girl with cyclic neutropenia was examined by electron microscopy. In the nonneutropenic phase, mature polymorphonuclear neutrophils had numerous bundles of filamentous inclusions in both cytoplasms and nucleus. Primary granules were slightly increased in number. Similar filament-like inclusions also have been reported in some cases of hemopoietic dysplasia; however, our case showed no abnormality in chromosomes, no thrombocytopenia, and no leukemic change.