Sunday, February 28, 2016

Case of the Week 387

This week's case was generously donated by Dr. Heidi Lehrke. These objects were seen in a lymph node aspirate specimen.

May-Grunwald-Giemsa, 600x
May-Grunwald-Giemsa, 1000x

How did they get into the specimen?

Saturday, February 27, 2016

Answer to Case 387

Answer: Giardia duodenalis (a.k.a. G. intestinalis, G. lamblia) trophozoites

This Giemsa-based stain nicely highlights all of the diagnostic features of Giardia trophozoites, including the flagella, which are not usually seen so well in trichrome or iron hematoxylin-stained stool preparations. The annotated image below shows some of the key diagnostic features:

Now to answer the important question that many of you asked - what are Giardia trophozoites doing in a lymph node?(!) Kudos to Anon, Florida Fan, and William Sears for correctly suggesting that the Giardia were a contaminant from the sampling method that was used.

What I didn't tell you is that the lymph node aspirate was performed using ultrasound-guided endoscopic biopsy. An endoscope was passed down the patient's esophagus, through their stomach and into the duodenum. Then, an aspirating needle was threaded through the endoscope and was used to take a sample of a neighboring lymph node by passing through the duodenal wall. Mystery solved!

This is the second case that I've seen of giardiasis detected incidentally during this procedure in the past 10 years, so it's important to understand how specimens are obtained.

Thank you for all of the great comments on this case. And thanks again to Dr. Heidi Lehrke for donating these beautiful pictures.

Saturday, February 20, 2016

Case of the Week 386

This week's case was discovered by the awesome techs in my lab while examining a concentrated wet-preparation from a stool specimen submitted for routine parasite exam. This is the only one of these objects identified. No further history was available.

100x magnification

400x magnification

Identification? What is the significance of this finding?

Friday, February 19, 2016

Answer to Case 386

Answer: Mite, not further identified.

It is difficult to identify this mite to the genus level based on the images shown. However, it is clear from the images that this is not Sarcoptes scabei or Demodex spp., two well-known human mites. Therefore, we are left with several options for identification:
1. This is a dust mite that was inadvertently swallowed.
2. This is a cheese mite or other mite commonly found in food.
3. This is a zoonotic mite that was accidentally ingested (none of which cause intestinal infection)

Therefore, this can be considered an incidental finding without clinical significance.

Monday, February 15, 2016

Case of the Week 385

This week's case was donated by an internal medicine resident, who passed the object shown below in his stool. He reported intermittent post-prandial abdominal pain and loose stools for several years, and a complete blood count 2 years ago showed peripheral eosinophilia. He has an extensive travel history, including trips to regions of Asia and Africa, where he ate the local food.

He unfortunately didn't save the specimen to submit to the laboratory since his wife was too grossed out and flushed it!

This resident now wants to know what to do next.

1. What is your presumptive identification from these photographs?
2. What is your advice for further identifying the nature of this object?

Sunday, February 14, 2016

Answer to Case 385

Answer: Tapeworm, probable Taenia species. Unable to confirm due to lack of specimen.

Wow, there were a lot of great answers (and debate) on this case, and I found it interesting to see that many of the comments were also things that I considered when trying to identify this worm from just the available photographs. The specimen is obviously a long segment of tapeworm proglottids, and the two main worms in the differential are Taenia sp. and Diphllobothrium sp. The factors in favor of each are listed below:

In favor of Diphyllobothrium: long segment of proglottids, many of which are broader than they are long.

In favor of Taenia: Some proglottids are longer than they are wide (recall that immature Taenia proglottids are shorter), and there are no visible central uterine rosette structures as expected with Diphyllobothrium. In my experience, fresh Diphyllobothrium proglottids have a dark, prominent central uterine rosette which is notably lacking here (see cases 246 and 345) - and this case was certainly fresh! Therefore, I favored that this was Taenia rather than Diphyllobothrium.

Unfortunately the specimen was not available for examination, and 3 follow-up ova and parasite stool exams did not reveal any eggs. Interestingly, all 3 specimens were positive for many Blastocystis hominis, and the patient had been experiencing irritable bowel-like syndromes for months. However, his symptoms resolved after treatment with praziquantel (for the tapeworm) and therefore he opted not to treat the Blastocystis. 

So after counselling the patient against eating undercooked fish, pork and beef in the future, no further follow-up was thought to be necessary. There is a very small risk of cysticercosis in this patient (or family members) due to eggs that he was likely shedding in his stool, so he will also keep this in mind and monitor himself and his family for symptoms. Finally, there is still the unresolved question of what was causing the patient's eosinophilia. That clearly deserves further work-up and suggests infection with another worm (e.g. Strongyloides stercoralis), so additional testing and/or treatment is indicated.

Sunday, February 7, 2016

Case of the Week 384

We're on a roll with arthropods! This week's case was donated by Dr. Ellen Stromdahl. This arthropod was removed from a patient and sent to her lab for analysis. It was beautifully photographed by Graham Snodgrass.

Bonus points if you can tell what is going on with this tick (hint, it's a rarely-captured stage of the life cycle).

Saturday, February 6, 2016

Answer to Case 384

Answer: Amblyomma americanum, molting nymph.

This is an amazing case because it demonstrates the rarely-seen stage of a nymph molting into an adult female. Note that the outer skin (exuvium) is still present, including the nymphal scutum. We can also see the body of the adult beneath the outer skin, and identify the adult scutum with characteristic macula of Amyblyomma americanum. So we have a tick with 2 scuta!

Sadly, the tick died before it could split the nymphal exuvium (outer skin) and emerge.
Thanks again to Dr. Stromdahl for sharing this case with us!