Case #346 – April, 2013

A 21-year-old exchange student from Nepal sought medical attention for intermittent diarrhea associated with mild abdominal cramps. A stool specimen was collected for laboratory testing in low viscosity polyvinyl alcohol (LV-PVA). A smear was made from the preserved stool and stained with trichrome. Figures A–D show what was observed in moderate numbers at 1000x magnification with oil; Figures A and B show the same object in different focal planes. The size of the objects ranged from 15-20 micrometers in diameter. What is your diagnosis? Based on what criteria?

Figure A

Figure B

Figure C

Figure D

The organisms observed were cysts of Entamoeba polecki, which is generally considered to be a nonpathogenic amoeba that can reside in the large intestine. Morphologic features shown included:

cysts within the size range (9-24 micrometers) for the species.
the presence of a large, irregular nucleus with a pleomorphic karyosome.
the presence of numerous irregular, red-staining chromatoid bodies.