Answer to Case 37

Answer: Wucheria bancrofti

Ok, I admit this was a hard case. There are several morphologic features present in these images to point you to an identification; unfortunately, some are conflicting. However, this is a real case and one that initially stumped us in the laboratory as well. Below are the steps I use for speciating microfilariae based on morphologic features:

First, I look for is the presence or absence of a sheath. Only 3 microfilariae have a sheath, so this immediately helps to focus your answer. For those of you that like memory aids, you can remember the 3 sheathed microfilariae by the following phrase: Wears Long Britches. The first letter of each word (W.L.B.) is the first letter of each organism: Wucheria bancrofti, Loa loa, and Brugia spp. Think of the "long britches" as the sheath over the worm's "leg".

If you identify the sheath, then look to see if the sheath stains with giemsa. The sheath of W. bancrofti and L. loa doesn't usually stain, and thus appears as a negative image, while the sheath of Brugia is usually bright pink. The sheaths of the first 2 organisms do stain pink with hematoxylin and eosin, so it's important to know what stain you're looking at (shame on me for neglecting to include this information).

This is where most will get out their atlases and look up the other specifics such as length of the worm, position of nuclei relative to the tail, characteristic of the nuclei and the tail, and the size of the cephalic space. Finally, travel history is essential, since the filarial worms have different geographic distributions.

So for this case, the overall length (approx. 300 microns), presence of a sheath, short cephalic space, and lack of nuclei in the narrow pointed tail indicated that this was W. bancrofti. Furthermore, the patient was from Africa, and had no history of travel to Asia, which would be expected to make a diagnosis of Brugia spp. The only feature that didn't quite fit was the fact that the sheath was stained pink with giemsa. Well, I guess you can't have it all....

Thank you to everyone who wrote in on this case. It just goes to show that real-life is rarely as easy as the textbooks.

Case of the Week 36

The following are touch-preps from a brain biopsy. Identification? (CLICK ON IMAGES TO ENLARGE)

Answer to Case 36

Answer: Toxoplasmosis; tachyzoites of Toxoplasma gondii seen.

This was a very challenging case since the multiple small objects (the tachyzoites) blended in with the surrounding tissue. However, if you click on the second image (also shown below), you get a larger view where it is easier to make out the organisms. I've added some arrows to highlight 2 of the tachyzoites that have a particularly nice arc shape. (CLICK ON THE IMAGE TO ENLARGE)


I posted this case because it is what you may expect to see in real life. When available, the clinical history, serology and radiology can help support the diagnosis. Thanks to everyone who was brave enough to write in on this case!

Case of the Week 35

Name 2 important histologic findings in the following bladder biopsies. (CLICK ON IMAGES TO ENLARGE)

Answer to Case 35

Answer: Urinary schistosomiasis with Schistosoma haematobium and adenocarcinoma of the bladder.

I admit that it wasn't quite fair to expect a diagnosis of cancer on just a few fields, but having seen this whole case, I can confirm that this is indeed adenocarcinoma. This is an unusual case, since schistosomiasis is usually associated with squamous cell carcinoma and not adenocarcinoma. However, it could be that the two findings are completely unrelated.

Of interest, you can see the terminal spine on one of the partially calcified eggs in the middle image, confirming that this is S. haematobium.

Case of the Week 34

Here is a simple identification. Feel free to be as general or as specific as you like, based on your expertise (and interest!).

Answer to Case 34

Wow, what a great response I had to this case! It is a beautifully ornamented tick, so I guess I'm not too surprised that it caught people's interest.

This is a male Amblyomma variegatum, also known as the Tropical African Bont Tick. It is found in the tropics and subtropics, including some islands of the Caribbean. You might notice from the photo that it has long mouth parts. Because of this, it tends to leave large (and painful) bite wounds.

It is a vector of several organisms causing veterinary disease (such as Heartwater fever), as well as Rickettsia africae, the agent of African tick-bite fever, and Crimean-Congo hemorrhagic fever virus. It may also carry a number of other viruses such as Dugbe, Thogoto, Bhanja , and Jos.

Congratulations to Karma453 for the correct answer, and to Anonymous for the follow-up answer. Also, special bonus points to F. and W. for their creative guesses that made me smile.

Case of the Week 33

The following lymph node biopsy was taken from a boy with no travel history outside of the U.S. He had presented with acute onset of fever and lymphadenitis.
Diagnosis? What is your differential diagnosis? (CLICK ON IMAGES TO ENLARGE)
Images courtesy of Dr. Thomas Trainer

Answer to Case 33

Answer: Toxoplasma gondii lymphadenitis. This is a rare case in that cysts are not typically seen in the affected lymph nodes. Instead, pathologists rely on the classic pathologic features (e.g. lymph node architecture and pattern of inflammatory cells) to suggest the diagnosis, which should then be correlated with clinical features and serologic tests.

Findings that may mimic the cysts of T. gondii include T. cruzi pseudocysts and macrophages with Leishmania spp. amastigotes or Histoplasma capsulatum yeasts.

Case of the Week 32

The following was extracted from the arm of a traveler to South America. Identification?