Case #203 – May, 2007
Giemsa-stained thick and thin blood smears were examined as part of a screening protocol for refugees from a country that has areas of ongoing malaria transmission. Figures A and B were captured from the thick smear; Figures C and D were captured from the thin smear. What is your diagnosis? Based on what criteria?
No parasites were seen on the smears; the structures were artifacts. These structures, known as Howell-Jolly bodies, are remnants of nuclear material (chromatin) of the red blood cell. The presence of Howell-Jolly bodies indicates that the patient either does not have a spleen, or their spleen is not functioning correctly; the spleen typically filters these bodies.
Features that indicated these structures were artifacts were:
- On the thick blood smear the Howell-Jolly bodies appear round and dark-blue, or slightly red. Actual Plasmodium sp. parasites may have some yellowish pigment and blue cytoplasm.
- On the thin blood smear the Howell-Jolly bodies appeared as round, dark blue or bluish-black structures. A view of the thin smear helped determine that these structures were artifacts, not parasites.
Figures A and B below are from a different case in which the patient was positive for Plasmodium sp., but also had Howell-Jolly bodies.
- In Figure A the black arrows point to the Plasmodium sp. parasites and the blue arrows point to the Howell-Jolly bodies in a thick smear.
- In Figure B two Plasmodium sp. parasites are visible (black arrows) as are the Howell-Jolly bodies (blue arrows).
Thick smears are useful for screening for Plasmodium spp. and Babesia sp. Follow-up examination of a thin smear is always recommended to confirm the presence and identification of possible parasites.
Images presented in the DPDx case studies are from specimens submitted for diagnosis or archiving. On rare occasions, clinical histories given may be partly fictitious.
DPDx is an educational resource designed for health professionals and laboratory scientists. For an overview including prevention, control, and treatment visit www.cdc.gov/parasites/.