Case #528 – November, 2020

A 42-year-old State Park employee sought medical care due to fatigue, insomnia, intermittent bloating, and mild anemia. He provided additional information that he often ate various plants (nuts, seeds, and berries) he encountered while on patrol. A stool specimen was collected and processed for ova and parasite (O & P) examination. Figures A and B show what was detected in moderate numbers on a wet mount. Size of the objects was approximately 20 micrometers in diameter. What is your diagnosis? Based on what criteria?

Figure A

Figure B

The objects of interest were artifacts and appear to be pollen grains of some type. Morphologic features shown in the images were:

Visible striations and small size might be misinterpreted for Taenia sp. eggs although the size is below the range (30-35 micrometers for Taenia sp. eggs).
Absence of hooks/hooklets within the structure also rules out Taenia sp. eggs.
Scalloped/textured exine (outer wall), with or without apertures (openings; can appear as pores or fissures); entine (inner wall) bounding cytoplasm, which does not feature any structure visible on light microscopy.

Pollen grain morphology is diverse but usually easily distinguishable from helminth eggs and protozoal cysts, because pollen grains have apertures, which appear as pores or colpi (fissures), and many species feature a geometric, symmetrical arrangement of such features.