Monday, April 23, 2018

Case of the Week 491

This week's case is courtesy of Dr. Delgado and the Yale Pathology department. The patient is young adult male with extensive travel throughout Europe, Central America and Africa, who presented fever, drenching night sweats, extreme fatigue, cervical lymphadenopathy and splenomegaly. CBC showed pancytopenia. The following are from the H&E-stained bone marrow biopsy and Giemsa-stained aspirate.


Monday, April 16, 2018

Case of the Week 490

This week's case is generously donated by Florida Fan. The following object was submitted to the laboratory for identification. It had been retrieved during colonoscopy from the cecum of a 40-year-old man.


Sunday, April 15, 2018

Answer to Case 490

Answer: Female Trichuris sp.
The most likely etiology is T. trichiura. However, as several readers mentioned, human infection with T. vulpis has rarely been reported and the adult worm has a similar appearance. The two worms are differentiated primarily by their eggs, with T. vulpis eggs being nearly twice as large as T. trichiura eggs. The only eggs we see in this case are immature and intrauterine; therefore it is not possible to use the eggs to help us differentiate the two worms.

Here are some of the key diagnostic features of this case:
Note that the head is at the slender end (all the better for embedding into the large bowel mucosa), while the larger end (containing the uterus and eggs) hangs free in the bowel lumen. We can tell that this is a female worm because of the eggs in the uterus (below) and because the tail is not coiled like a male's tail would be.

Monday, April 9, 2018

Case of the Week 489

Happy Unicorn Day! (yes, there really is such a thing).
This was seen in a trichrome-stained stool specimen. It measures approximately 19 micrometers in diameter, not including the 'horn'.
These were also seen in this specimen:

Identification? Images are courtesy of Emily Fernholz, MLS(ASCP).

Sunday, April 8, 2018

Answer to Case 489

Answer: Entamoeba coli or 'uniamoeba'!
While this case shows a beautiful trophozoite 'unicorn' for national unicorn day, it has an atypically-large karyosome which makes it challenging to identify it as E. coli. I therefore added some additional trophozoite photos from this case. Note the smaller, eccentric karyosome and clearly clumped peripheral chromatin seen in the following trophs:
As Idzi pointed out, this one looks like a dog's head!
The cysts were clearly consistent with E. coli, containing >4 nuclei (8 in the mature cyst). 

Monday, April 2, 2018

Case of the Week 488

Happy April! It's time for our first case of the month by Idzi Potters and the Institute of Tropical Medicine, Antwerp.

The patient is an adult male without known travel history who passed the following worm-like structure. It was placed in physiological saline solution and sent to the laboratory for identification.

In the lab, a drop of the saline solution is also examined microscopically, revealing the structure in the picture (size: 32 µm).

Diagnosis please?

Sunday, April 1, 2018

Answer to Case 488

Answer: Taenia sp.
Molecular testing showed this to be Taenia saginata.

There was a lot of great discussion regarding the differential on this case. Some of the key features were as follows:
1. Large size - although not given, you can see that this is a large tapeworm that fills the Petri dish. Even if this was a small Petri dish, the size would be most consistent with Taenia spp., Diphyllobothrium spp., and possibly Hymenolepis diminuta.

2. Size/shape of proglottids - this is one area where the ID gets tricky. Mature proglottids of H. diminuta and Diphyllobothrium are wider than they are long, whereas mature proglottids of Taenia spp. are longer than they are wide. The caveat is that immature proglottids of Taenia (as seen in this case) are also wider than they are long. Thus all 3 of these worms are in the differential. However, the proglottids of H. diminuta are very short and not like the ones shown in this case. Therefore, this diagnosis is less likely, leaving us with Diphyllobothrium and Taenia species as considerations.

3. Internal proglottid structures - this is a very helpful feature of this case since an internal 'rosette-shaped' uterus (consistent with Diphyllobothrium) is NOT present, but instead the opening to the lateral genital pore can be seen; the latter is consistent with this being a Taenia sp. proglottid.

Taenia sp. (this case); arrows show openings to lateral genital pores:
Diphyllobothrium sp. shown for comparison showing central rosette-structured uterus:
H. diminuta showing extremely short proglottids (from CDC DPDx):
4. Morphology of the eggs - another tricky factor here! This egg clearly contained a hooked-onchosphere, but it lacked the outer shell of Hymenolepis and the outer striated wall of Taenia spp. As mentioned above, this was a Taenia sp., and thus the lack of the thick striated outer shell can be attributed to the immature state of the egg (matching the immature proglottids). 

Monday, March 26, 2018

Case of the Week 487

This week's case just came through my lab. The video and photos are courtesy of my excellent technical specialist, Heather Rose. Identification?

It was hard to get a still shot of this little arthropod:

Sunday, March 25, 2018

Answer to Case 487

Answer: Cimex lectularis, or as Sheldon Campbell said, "Eew, bedbug!".

Eew, indeed. As someone who has been in hotel beds more than my own recently, I have perfected the 'bed bug check' of the hotel room. I have been fortunate so far NOT to have found any of these little pests in my hotel room. I am now on my way to Belize for a vector-borne disease capacity-building project and hope that the trend continues.

Thanks to William Sears and Florida Fan who shared some nice stories about C. lectularis, and its cousins, the bat bugs (check them out in the comments section).

Blaine also helpfully pointed out that you *might* be able to see the ecdysial scar on the pronotum, which would indicate that this is a nymph rather than adult female as I had originally indicated.  I believe he is correct and so I took our my description of gender from the initial case description.

Monday, March 19, 2018

Case of the Week 486

For this week's case, I'm going to take advantage of whole slide imaging technology via the cloud. The patient is a middle-aged male smoker from the southern United States who presented with shortness of breath, and imaging revealed a lung nodule. Because of concern for malignancy, the nodule was excised and sent to pathology for analysis. Here is a representative image of the nodule:

Click HERE to zoom in and explore this slide! You don't need any special password or software to view the case.


Sunday, March 18, 2018

Answer to Case 486

Answer: Dirofilaria sp., most likely D. immitis, given the location in the lung.
As Blaine pointed out, this case is unusual in that it features an adult rather than larval worm, as evidenced by the presence of reproductive organs. While it's not uncommon to see adult Dirofilaria in subcutaneous lesions (e.g. caused by D. tenuis), it's very uncommon (but not unheard of) to see adults in the lung. Some of the diagnostic features are highlighted in the image below.

Thanks to everyone who gave the whole slide imaging technology a 'whirl', even if histopathology is not your area of expertise.

Monday, March 12, 2018

Case of the Week 485

This week's case is donated by Dr. Luis Fernando Solórzano Álava from Ecuador. The 'patient' is not a human, but rather an Ecuadorian snail. However, the parasite shown is indeed very pathogenic to humans and has a predilection for the central nervous system.
You can also see the video HERE.

Any thoughts on its identification?

Sunday, March 11, 2018

Answer to Case 485

Answer: Angiostrongylus cantonensis,  the rat lungworm

As many of you mentioned, the clues to the identification of this parasite are the characteristic morphology of the larvae, the host (snail), and the predilection of the parasite for the human central nervous system (CNS). A. cantonensis can infect snails and slugs, which if accidentally ingested, can lead to debilitating, even fatal, eosinophilic meningitis in humans when the immature worms migrate to the CNS and die. Human infection can also be acquired through ingestion of infected paratenic hosts such as crabs and fresh water shrimp, and may potentially be acquired through ingestion slug/snail slime containing L3 larvae on inadequately-washed vegetables.

Although this infection was first identified in Asia, it has spread throughout the Pacific basin, and is also found in parts of Africa, the Caribbean, and Ecuador. Florida Fan points out that the related organism, A. costaricensis, causes intestinal angiostrongyliasis, and is found in parts of South and Central America. Most cases of A. costaricensis infection are reported from Costa Rica

Here are some nicely-labelled images that Dr.  Solórzano Álava created for this case that demonstrate the key morphologic features. I find the pointed tail to be especially helpful!


Monday, March 5, 2018

Case of the Week 484

It's the first of the month again - time for a case from Idzi Potters and the Institute of Tropical Medicine, Antwerp!

The patient is a frequent traveler who recently returned from Kenya where he participated in a game tracking excursion. He now presents with high fever, malaise and headache. The following were seen in a preparation of unfixed blood:

You can also see the video on YouTube:

A Giemsa-stained thin blood film was also performed and showed the following:

Sunday, March 4, 2018

Answer to Case 484

Answer: Trypanosoma brucei
This is most likely T. brucei rhodesiense based on:

  1. The patient's recent travel to Eastern Africa (Kenya),
  2. His participation in a game tracking excursion (classic history given that wild ungulates are the reservoir for this subspecies),
  3. His rapid onset of symptoms, and
  4. The very high (!) parasitemia

Be sure to check out the video which show the characteristic 'auger' like motility of the trypomastigotes (i.e. rotating along its long axis).

Thanks to everyone who wrote in with the excellent comments. A lot of good points were raised by all. Ali Mokbel mentioned that we can't exclusively rule out T. b. gambiense, given that the patient is a frequent traveler and may have been to West Africa. Idzi also reminded us that the trypomastigotes of T. brucei are indistinguishable from those of T. rangeli, a non-pathogenic New World trypanosome which can occasionally infect humans. Fortunately, we can tentatively rule out these other species/subspecies based on the very high parasitemia and patient's symptoms. If there was any question about the identification (e.g. based on the patient's travel history), sub-species determination using PCR could be performed.  

Finally, LS reminded us of the importance of determining whether the patient had central nervous system involvement since that would change the therapy. If suspected, a lumbar puncture could be performed to look for trypomastigotes.

For our students of parasitology, the following contains some general information about trypomastigotes, the most trypanosome stage seen in peripheral blood. Trypomastigotes are extracellular, unlike Plasmodium parasites, and may be seen 'swimming' between the red blood cells as in this case (check out Idzi's really cool video!). Although they have a somewhat 'worm-like' appearance, they are protozoa (not helminths), and can be easily differentiated from microfilariae by their small size (14 to 33 micrometers in length). They have a kinetoplast at their posterior end (arrows in image below) and a centrally located nucleus. A flagellum arises from the basal body (associated with the kinetoplast) and travels along the long axis of the trypomastigote as an undulating membrane. It projects from the anterior end as a free flagellum (arrow head, below), and provides the characteristic 'auger-like' motility of the trypomastigote.
Note that the flagellum is at the anterior end of the trypomastigote, and not the posterior as many would expect!

The size of the kinetoplast is very useful for differentiating the trypomastigotes of T. brucei/T. rangeli from those of T. cruzi. As you can see from the image below, the kinetoplast of T. cruzi is much larger:

Monday, February 26, 2018

Case of the Week 483

This week's case was donated by Dr. Lars Westblade. The patient 'coughed' up the following worm (which was still moving!) after approximately 1 month of intermittent hives.

The posterior end was damaged unfortunately, but here is the anterior end:

What is your differential diagnosis?

Sunday, February 25, 2018

Answer to Case 483

Answer: Probable anisakid (Anisakis sp., Pseudoterranova sp., or Contracaeceum sp.)

There was a lot of great discussion on this case! While we can't definitively rule out a migratory immature Ascaris lumbricoides (crawling up from its usual intestinal location), the size of the worm, morphology, and patient history are most consistent with this being an anisakid larva. Anisakiasis occurs in humans following consumption of undercooked fish or seafood containing coiled anisakid larvae. The larvae cannot mature in humans but still have the potential to cause significant problems for their unintended human host. In the 'best case scenario', the larva dies and is passed in stool. If seen by the patient, it may be submitted to the laboratory for identification. A less optimal scenario is what was seen in this case where the live larvae crawls up the esophagus and is 'coughed up' or expelled out of the mouth.  While no doubt disturbing, this is still better than the alternative, in which the larva burrows into the gastric or intestinal mucosa, causing significant pain for the host. If the larva is not immediately removed, the patient may experience symptoms for an extended period of time until the larva dies and is absorbed by the host. Rarely, the larva will penetrate the wall of the stomach or intestine and enter the peritoneal cavity, wreaking further havoc. A final, but equally important, complication of exposure to anisakid larvae is development of an allergy to anisakid proteins. This can occur regardless of whether the larva is alive or dead. Sensitized individuals must avoid anisakid-infected fish or risk experiencing serious allergic, or even anaphylactic, reactions, upon re-exposure.

 Anisakid larvae can be identified by a few features: they are ~3 cm in length, have 3 fleshy lips just like A. lumbricoides, and also have a very small 'boring' tooth on the anterior end (which can be very difficult to see). Some species also have a posterior spicule called a mucron which is easier to identify. Ascaris doesn't have a boring tooth or posterior mucron, so these are helpful features when seen. Unfortunately the posterior end was damaged during removal so we weren't able to examine it.

What I found to be very interesting about this case was the history of hives, suggesting an allergic reaction to the larva. The time frame of symptoms was also interesting - the patient experienced hives for ~ 1 month before expelling the worm, which indicates that either the larva was present all of that time without causing any gastrointestinal symptoms, or the patient had ongoing exposure to anisakids through his diet. I'd be curious to know - have any of my readers run into a similar case? This is actually the second case I've seen where the patient had been symptomatic for several weeks after presumed exposure and before expelling the larva. This leads me to think that some larva can exist in the host for weeks without burrowing into the gut lining.  Please let me know what your experience has been!

Monday, February 19, 2018

Case of the Week 482

This week's case was donated by Dr. Paul Green. The following worm was removed from the eye of a Nigerian man, and was noted to still be moving after removal:
 Although it was damaged during removal, the key diagnostic features are still visible.

Anterior end:

mid-body with disrupted area:

Closer look at the internal organs:

Posterior end:
Identification? What additional specimen could confirm your diagnosis?