Case #320 – March, 2012

Stool specimens were collected from Haitian refugees as part of a screening program for intestinal parasites. Stool was collected in polyvinyl alcohol (PVA) and 10% formalin and sent to the county public health lab for routine ova-and-parasite (O&P) examination. Figures A–D show what was observed in moderate numbers from one of the patients on a trichrome-stained slide from the PVA-preserved stool. All images were captured at 1000x magnification. What is your diagnosis? Based on what criteria?

Figure A

Figure B

Figure C

Figure D

This case showed a mix of two intestinal protozoa, Endolimax nana and Blastocystis hominis. Both species were shown in all four images. Diagnostic features included:

ovoid cysts of E. nana presenting with 2-4 nuclei, each with a discrete karyosome (Figures A–C; there was also a cyst out-of-focus in the upper edge of Figure D).
trophozoite of E. nana presenting with a single nucleus containing a large, central karyosome and no peripheral chromatin (Figure D).
cyst-like bodies of B. hominis presenting with a large, central body surrounded by a narrow rim of cytoplasm containing nuclei and inclusion bodies (Figures A–D).

More on: Blastocystis hominis; Endolimax nana

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.