Case of the Week 805

This week's case was generously donated by Dr. Karra Jones, and features H&E histopathologic sections of intestine from patient with intussusception. Upon close examination, the culprit behind the intussusception can be seen:

What is your diagnosis?

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Case of the Week 804

This week's case is by Florida Fan, and represents a nearly 'picture perfect' representation of a particular filarial species in a peripheral blood smear. What is your identification? For students, residents, and fellows - this is a classic, and definitely fair game on exams!

Answer to Case 804

Answer to the Parasite Case of the Week 804: Brugia sp. microfilaria, favor B. malayi 

As noted by Idzi and others, this is a textbook example of Brugia sp. microfilaria, with beautiful terminal and sub-terminal nuclei and a characteristic long cephalic space. However, Idzi rightly recommends caution in committing to a species since B. malayi and B. timori can have a very similar appearance. He notes that "to decide which one, either geographical information is needed (B. timori is more restricted to the Lesser Sunda Islands of the Indonesian archipelago - from Bali over Timor to the Tanimbar Islands - while B. malayi is more widespread in South-East Asia), or information about the stain for the blood film (both Brugia species have a sheath in fact, but if the smear is stained with Giemsa, the sheath of B. timori is usually not visible).  

While we don't have an exposure history in this case, the stain is Giemsa, which points us to B. malayi. However, I consider the sheath staining to be a soft diagnostic feature, as I've seen this type of faint pink staining with Wuchereria, and not all B. malayi sheaths stain with Giemsa. 

Since the sheath staining is not reliable, we must use the other criteria for differentiating B. malayi and B. timori as follows: 

• B. malayi microfilariae are 175-230 micrometers long in stained blood smears, while B. timori microfilariae are ~310 micrometers. The current case appears to be in the former range, but it is a bit hard to tell from the image.
• B. timori microfilariae have a longer cephalic space and a more single file nuclei in the tail.
• Classically, the sheath of B. malayi microfilariae is deep pink on Giemsa-stained blood films, while the sheath of B. timori does not stain with Giemsa.

Given these features, I think we can make a tentative diagnosis of B. malayi, and try to obtain more clinical history.

Check out Idzi's previous beautiful cases of B. malayi and B. timori on this blog. You can find several more B. malayi cases by searching in the upper left-hand search bar.

The CDC DPDX also has some nice examples of B. malayi and B. timori.

Thanks again to Florida Fan for donating this beautiful case.

Case of the Week 803

For this week's case, we have a worm submitted from an otherwise asymptomatic teenager. No further history was provided. What is your identification, and how would you sign this case out?

Based on this gross examination, we dissected the worm and was able to get the following eggs:

Answer to Case 803

Answer to the Parasite Case of the Week 803: Toxocara species, adult female. Humans are NOT a host for this life cycle stage of the parasite. Therefore, as Philip, Anastasia, Anatoly, HCLM Fan, and others mentioned, the most likely scenario is that this worm came from a family pet instead of the teenager. Less likely, the teenager could have swallowed the worm and its finding in stool represents spurious passage. Unfortunately, we were not able to get any additional history in this case. Hopefully this result was reassuring and helpful to the patient and family. 

Although this worm resembles the large human intestinal worm, Ascaris lumbricoides, it can be differentiated in this case by two main features:

First, this worm has pronounced lateral alae, which are not found in Ascaris lumbricoides. (Lateral alae are found in Enterobius vermicularis, but that worm is much smaller and can therefore be excluded).

This alone would have been sufficient to rule out a human parasite. However, we also have the eggs to confirm the identification of Toxocara sp. Note their thick outer wall and characteristic pitted shell:

Thanks again to those who wrote in with their comments. This case shows why it is helpful to be familiar with common zoonotic parasites. Additionally, the larvae of Toxocara can cause visceral larva migrans if the eggs are ingested by a human host. Therefore, identification may be helpful for the pet to be treated and reduce the household risk.

 

Case of the Week 802

Apologies everyone for the delay in posting a case. I've been travelling a lot and just returned from South Korea. While I was there, I was offered the following dish consisting of raw crab. If I had chosen to eat it (which I didn't), which parasites could I have acquired?

 

Answer to Case 802

Answer to the Parasite Case of the Week 802: No significant parasite risk.

But wait, you may say, what about paragonimiasis???

As noted by Anatoly, Kim Tae Yun, and others, these are marine crabs rather than fresh water - an important distinction! Eating undercooked freshwater or estuarine (brackish) crabs could indeed lead to paragonimiasis, and this was historically an endemic infection in Korea. However, the risk from eating undercooked marine crabs is relatively low. According to Kim Tae Yun, "Most Korean people enjoy the food so called GEJANG (crab soaked in soy sauce)...And the GEJANG in the photo looks very delicious." 

What do you think?

Anisakiasis and gnathostomiasis are hypothetical risks from eating freshwater crabs as well, but highly unlikely as crabs are not the typical hosts for the associated parasites.

I must admit that I chose not to eat this dish for two reasons: first, I was uncertain about the type of crab offered, and second, I'm not a huge fan of raw seafood. However, the food I did eat, including a crab hotpot and kimchi pancake, were absolutely delicious.

Thank you all for sharing your own experiences.

Case of the Week 801

This week's case was an interesting finding from microscopic examination of skin scrapings. What is your diagnosis? And what forms are you seeing?

Answer to Case 801

Answer to the Parasite Case of the Week 801: Sarcoptes scabei, adult and juvenile mites, eggs, and feces (scybala). 

Florida Fan so nicely described the findings here as follows: "Boy, this should give the host quite an itch. We find the feces or scybala, the egg, the premature or developing stage before eclosion and finally the mother mite itself. Sarcoptes scabiei and its family members not only infest humans as itch mites but also infest other warm blooded animals as mange as well. Hopefully the Easter bunnies are spared from its cuniculi species."

Here is a closer view of two eggs (arrows) and numerous fecal pellets (the small, oval, granular structures):