Sunday, October 2, 2011

Answer to Case 178

Answer: Cyclospora cayetanesis oocysts

The size, history, and strong acid fast positivity are consistent with a diagnosis of cyclosporiasis. However, one viewer points out that the coccidians are inherently difficult to capture in a single photograph since the cellular features may not be well defined, and that fungal artifacts may still be in the differential. Therefore, I've also included the following wet-prep image showing an oocyst from this same case (CLICK ON IMAGE TO ENLARGE). From this image, the round shape and internal structures can be appreciated.

When examining modified acid fast stains, it is also important to note that the size of the stained objects is also important, since Cryptosporidium spp. oocysts have a very similar appearance, but are smaller (4-6 microns in diameter).

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