This week's very timely case was donated by George at Memorial Sloan Kettering Cancer Center. The following objects were seen in a wet mount of a concentrated stool specimen. They measure less than 20 micrometers in dimension and do not have an apparent operculum.
Answer: not a parasite; most consistent with mushroom spores.
In this case, the spores were noted in the stool of an individual who had consumed morel mushroom spores, and therefore we can be more specific about the identification.
Mushroom spores are a convincing mimic of parasite eggs. They can be differentiated by a few features, however:
1. Their size is smaller than Enterobius vermicularis eggs - one of their closest mimics.
2. Although in the size range for some of the smaller trematode eggs (e.g. Clonorchis, Metagonimus), they lack an operculum.
Again, special thanks to George who donated these images and reminded me that it is now morel mushroom season!
Answer: Capillaria philippinensis
This case shows an adult worm containing characteristic eggs of C. philippinensis. Note that each egg has a striated wall and bipolar plugs.
Thanks to the CDC DPDx for the photo of the egg shown in the upper right hand corner of the above image.
One reader asked how you could tell C. philippinensis apart from C. hepatica, since both can infect humans. The biggest clue in this case is that the worm was found in stool, whereas the adult worms of C. hepatica are only found in the liver. There are also subtle features of the adult worm and eggs that allow the 2 species to be differentiated.
Thanks again to Mr. Huot for donating a case that we don't get to see very often in the United States.
Answer: not a parasite; most consistent with banana seeds.
This is something that we commonly see in my lab, and I've previously featured other examples of banana seeds on this blog. Here are the links to 2 previous posts: Case 139 Case 402
Because I've received some degree of skepticism when I've posted banana seeds in the past, I decided to conduct an experiment to see if I could recreate their appearance through some laboratory digestion techniques. So here was my process:
Step 1. Sacrifice my banana from lunch for the good of science
Note the small immature seeds that are seen in these longitudinal sections. A fun fact - the bananas that we buy in the grocery store have been bred so that the seeds never mature. Wild bananas have large seeds which make the fruit less pleasant to eat.
Step 2. Add bananas to pre-prepared tubes of proteinase K in buffer. (Unfortunately I didn't have any amylase which would have digested the carbohydrates in the banana. However, this was the best I could do to simulate the digestive process). Vortex to mix and then incubate at 56 degrees Celsius while gently shaking (the standard tissue digestion that we use for PCR pre-processing).
Step 3. Check regularly. I first checked every 10 minutes , but very quickly realized that this was going to be a long process. After the first 4 hours, this is how the banana sections looked:
Step 5. Final check - 48 hours. Success! I think that these look nearly identical to our clinical specimen. What do you think?
Close-up view of the seeds (look a lot like the previous cases):
Again, it's not a perfect match since the actual patient specimen was subjected to the entire gastrointestinal digestive process. However, the strings of immature seeds can clearly be seen. Here is how they look microscopically:
You can also appreciate the starch granules of the banana (taken using a 40x and 100x objective):
I hope you all enjoyed this experiment as much as I did!
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:
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).
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.
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
Count those branches more than
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.
Every week I will post a new Case, along with the answer to the previous case. Please feel free to write in with your answers, comments, and questions. Also check out my image archive website at http://parasitewonders.com. Enjoy!
The Fine Print: Please note that all opinions expressed here are mine and not my employer. Information provided here is for medical education only. It is not intended as and does not substitute for medical advice. I do not accept medical consults from patients.