Case of the Week 169

I have a challenging case for you this week!
During routine colonoscopy for colon cancer screening, endoscopists noted the following worm-like objects in the cecum:


One of these objects was removed and sent to surgical pathology where it was fixed in formalin, paraffin embedded, and sectioned for staining with hematoxylin and eosin. Unfortunately, no intact objects were sent to microbiology for identification. The portion of the object shown measures 2.5 mm. (CLICK ON IMAGES TO ENLARGE - YOU'LL WANT TO SEE THE DETAILS ON THIS ONE!)

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1000x original magnification

Answer to Case 169

Answer: Hymenolepis nana tapeworm

Shown here are classic proglottids and eggs (in utero) of Hymenolepis spp. The small size and probable presence of polar filaments is consistent with Hymenolepis nana (see images below).




As nicely stated by L.R., "adults only get to around 30-45 mm. The worm has an interesting life cycle flexibility - it can be transmitted via a direct transmission route from person to person as well as being transmitted by fleas which can serve as intermediate hosts/vectors."

As MicrobeMan correctly mentions, the eggs are somewhat distorted due to tissue fixation, processing and sectioning, and thus do not appear as spherical as would be expected in a stool preparation. They are also in utero, and some may be immature. An image of how the eggs typically look in stool can be seen at a previous post HERE.

Case of the Week 168

The following is a Giemsa-stained peripheral blood thin film from a 5 year old girl with fever and a swollen eye. She has recently moved with her family from Argentina.
Diagnosis?

Answer to Case 168

Answer: Trypanosoma cruzi trypomastigotes (flagellated forms)

Thanks to everyone who wrote in with the answer to this case - you were all correct!

EST2010points out that this organism "is transmitted through excrement from the Reduviid or 'kissing bug' found throughout S. America. Key differentiating features from African trypanosomes (T. brucei rhodesiense and T. brucei gambiense) include the very enlarged posterior kinetoplast, the curved 'C' shape and geography." Neuro_Nurse further notes that "the swollen eye is known as Romaña sign." So you all picked up on the clues that I gave you for this case.

Here is an image comparing the size of the kinetoplast between T. cruzi and T. brucei (the most important differentiating feature):

Although I've shown you the classic "C" shape of T. cruzi, note that this is not a reliable feature for identification, since T. brucei subspecies can also take on a "C" shape.

Case of the Week 167

We will resume next week with the new Parasitology Case of the Week.

Answer to Case 167

Answer: Giardia intestinalis (a.k.a. G. lamblia, G. duodenalis)
OR
As Tom writes "This looks like the rarely seen Giardia patrioticus, which is associated with outbursts of sometimes sulfrous emmisions, of which there is evidence in the background of the slide in this image."

Great Answer!