Revisiting Howell-Jolly Body-Like Cytoplasmic Inclusions in Neutrophils: A Report of Two Cases and Confirmation of Nuclear Origin

Howell-Jolly body-like inclusions in neutrophils have been reported in a handful of reports; however, their nuclear origin has never been confirmed to date. We report the presence of these cytoplasmic inclusions in two cases and confirm their DNA-based origin by fluorescent nuclear staining. Peripheral blood smears were manually reviewed by light microscopy and after 4',6-diamidino-2-phenylindole (DAPI) fluorescent staining via confocal microscopy. Methanol fixed peripheral blood smears were incubated with DAPI (Sigma Aldrich, St. Loius, MO, USA) and coverslipped with mounting media. DAPI-stained cells were imaged with a Leica SPE confocal microscope using a 405 nm excitation laser and a 63×/1.3 NA oil immersion objective. Optical sections spanning the entire cell thickness were acquired and maximum intensity projections were produced in ImageJ. Both cases described herein had Howell-Jolly body-like inclusions similar to those reported in the literature. Testing for relevant infectious etiologies was negative. Positive staining on fluorescence microscopy confirmed DNA-based origin of this cytoplasmic inclusion material. These DNA-based inclusions occur in the immunosuppressed patient and mimic infectious inclusions. While morphologically worrisome, recognition of these inclusions may prevent unnecessary treatment and testing in clinically appropriate patients.