Sunday, April 23, 2017

Case of the Week 443

This week's case was donated by Dr. Tom Grys. The patient is an immunocompromised man with hemophagocytic lymphohistiocytosis (HLH) and fever. He reports travel throughout the United States and Italy. Bone marrow biopsy revealed the following:


Saturday, April 22, 2017

Answer to Case 443

Answer: Leishmania amastigotes
This case shows the characteristic morphology of amastigotes within a macrophage. The arrow below highlights an amastigote in which the nucleus and kinetoplast can both be seen.
One of the most important teaching points about this case is that the patient acquired infection in Italy - a country that many physicians (especially in the United States) do not realize is endemic for Leishmania infantum. Of note, Leishmania infantum is nearly identical to L. chagasi, a pathogen found in the Americas, and some consider them to be the same organism (in which case L. infantum would have preference).

Sunday, April 16, 2017

Case of the Week 442

This week's case was generously donated by Dr. Bryan Schmitt and Kayla Kirby. The patient is a middle-aged man from West Africa who presented with a chief complaint of worms in his stool. Four tan-white objects were received in saline and an egg was expressed from one of them.


Saturday, April 15, 2017

Answer: Case 442

Answer: Taenia saginata proglottid and egg

This was a remarkable case in that the fresh proglottids clearly showed the characteristic uterine branching pattern without the need for clearing, mounting, or India ink injection. Instead, you can see all of the lateral branches coming off of the central uterine stem with surprising clarity:
By counting the uterine branches, you can differentiate Taenia solium from T. saginata/T. asiatica. 
Note that you should only count the primary branch points coming off of the central uterine stem. Also, it is important to count only on one side. As you can see from my line drawing above, there are ~15 branches that can be identified in this specimen, thus making this either Taenia saginata or T. asiatica. Given that this patient was from Africa, we can narrow the differential to T. saginata, the "beef" tapeworm. Upon questioning, the patient admitted to frequently eating undercooked beef, which is the route of human infection.

As a confirmatory measure, the proglottids were manipulated to release eggs like the one shown below, which confirm without a doubt that this is a Taenia proglottid. Note the characteristic morphologic features including internal hooklets (one is clearly seen) and thick outer wall with radial striations.
Here is a fun accompanying poem from Blaine Mathison:

If one eats undercooked meat in Africa it’s a general rule
It’s likely he will end up with proglottids in his stool!
As deeper into your ID you delve,
Count those branches more than twelve!
You’ll see it’s T. saginata, just like you learned in school!

Thank you again to Bryan and Kayla for donating this great case.

Monday, April 10, 2017

Case of the Week 441

This week's case was generously donated by Dr. Nipunie Rajapakse. The following object was passed in the stool of a teenage boy with recurrent fevers and constipation. His only travel outside of North America was Portugal and Hawaii. Treatment with an antihelminth was ineffective at alleviating his symptoms and follow-up stool exams were negative.


Sunday, April 9, 2017

Answer to Case 441

Not a parasite; most closely resembles a slice of onion/onion skin. If you do an internet search for sauteed onions, you will find many beautiful (and tasty looking) examples of similar-appearing structures.

This case is a great reminder that many food partially-digested objects can be seen in human stool specimens, and many of them (e.g. bean sprouts, bubble gum, citrus pieces, onion slices, tomato skins) can be seen an mistaken as parasites. The definitive way to differentiate these objects from true parasites is to look them under a dissecting microscopy and by light microscopy if necessary, examining the consistency and looking for eggs (as suggested by Michigan Micro).

Monday, April 3, 2017

Case of the Week 440

This week's case was from a young boy who had been unsuccessfully treated for pinworm infection. An apparent worm was submitted to the laboratory on a pinworm paddle (Swube®):

Given the unusual morphology, the specimen was cleared with Citrisolve and mounted on a slide for examination:

Identification? Many thanks to Florida Fan for donating this week's case!

Sunday, April 2, 2017

Answer to Case 440

Answer: Dipylidium caninum proglottid containing characteristic egg packets.

This is such a great case because it shows the characteristic morphology of this cestode, as well as how a clinical misdiagnosis (in this case, as pinworm) led to incorrect therapy, which was remedied following correct identification in the clinical microbiology laboratory. Thanks again to Florida Fan for donating this case. Here are some of the key features of this case: