Case #439 – March, 2017

A 29-year-old male immigrant from Nigeria presented to an emergency room with fever, splenomegaly, jaundice, and neurologic changes. Blood was drawn and used for a complete blood count (CBC) and complete blood chemistries panel which revealed anemia, thrombocytopenia, hypoglycemia, mildly elevated bilirubin and lactic acidosis. Figures A and B show what was observed on a Wright-Giemsa stained thin blood smear. What is your diagnosis? Based on what criteria?

Figure A

Figure B

This was a case of severe malaria caused by Plasmodium falciparum. Diagnostic features shown were:

normal sized infected red blood cells
parasite density estimated to be greater than 5% of red blood cells. Note that virtually all of the parasites present as compact trophozoites with pigment.
multiply infected red blood cells.
accolade/appliqué
an immature P. falciparum gametocyte (Figure B), also in a normal sized red blood cell.

This case demonstrates the abnormal morphology of parasites observed when blood smears for the diagnosis of malaria are not made in a timely manner. These parasites have continued to develop outside of the body within the collected blood tube prior to the diagnostic smears being made. Other observations included both infected and non-infected red blood cells showing crenation.

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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/.