Sunday, May 8, 2011

Answer to Case 160

Identification: Not a parasite; most likely uric acid crystals.
Congratulations to Dana who got this one right!

These crystals can cause quite a problem for the untrained cytopathologist, since they resemble parasite eggs and fungal conidia. However, as Luke points out, these are not parasite eggs because they have spines at BOTH ends, and not just one (as you would expect for Schistosoma hematobium eggs).

Other clues to tell us these are not parasite eggs are:
1. the cracked appearance of some of the crystals (parasite eggs may break open, but don't usually crack neatly in half)
2. Lack of internally staining structures (remember this is a pap stain, and true parasite eggs will typically stain)
3. Size variability and small size (smaller than what would be expected for S. hematobium eggs.

I've actually shown a picture a picture of these crystals before:
Click HERE to see the previous case.

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