Sunday, April 20, 2008

Answer to Case 18

Answer: Paragonimiasis involving the CNS.

This was definitely one of the harder cases I've shown so far. I tried to make it a little easier by telling you the size of the eggs (90 microns) and the location (brain). There are not many eggs that fall into this size range and are known to (rarely) involve the CNS. Schistosoma japonicum would be your main differential diagnosis.

The key to identifying these eggs is by recognizing the shouldered operculum. It is present on at least one egg in each image (shown by arrows). The eggs of Fasciola and Fasciolopsis spp. also have an operculum, but it is not shouldered and is very hard to identify in tissue sections. These eggs would also be larger than 90 microns. Of note, the eggs of S. japonicum are not operculated.

For interest, I also added an image demonstrating the egg contents, and an image where an egg is being ingested by a multinucleated foreign-body type giant cell (essentially a giant macrophage). CLICK ON THE IMAGES TO ENLARGE.

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