Monday, December 28, 2009

Case of the Week 99

Welcome back Readers to the last case in 2009! I think it is very fitting that this is Case 99, and that Case 100 will be the first case of 2010.

This case is a colon biopsy that contained an unexpected object:
For the non-pathologists, note that what we're seeing is a worm cut in cross-section. Use the internal structures to help you identify it. Another hint: notice that the worm portion shown is external to the intestinal mucosa.


Sunday, December 27, 2009

Answer to Case 99

Congratulations to everyone who recognized the bipolar plugs of the eggs inside this cross section of Trichuris trichiura. This was a tricky case, but the location of the worm helps (colon lumen), and the eggs are diagnostic. Although the eggs are reminiscent of hookworm (as suggested by one viewer), that is largely due to the fact that the cytoplasmic contents of the eggs have retracted from the wall (probably as an artifact of fixation). The thick wall and bipolar plugs are the most useful features.

Happy New Year to all of my parasitology friends!

Monday, December 21, 2009

Case of the Week 98

Here's a challenging case for you to start off the holiday week:
The following eggs were seen in a stool preparation from a 2 year old boy with vague abdominal pain. They measure approximately 50 microns in greatest dimension. Identification?

Sunday, December 20, 2009

Answer to Case 98

Answer: Hymenolepis nana eggs
Most people who wrote in with the answer to this were correct - these are good examples of the thin-walled H. nana eggs, with a central 6-hooked embryo, and 4 to 8 polar filaments radiating from thickenings of the envelope surrounding the embyro (onchosphere). The eggs measure between 30 to 50 microns in diameter.

H. nana, also known as the dwarf tapeworm, most commonly infects children, and is acquired through ingestion of eggs, or infected beetles (the intermediate host). The usual definitive host is a rodent.

Monday, December 14, 2009

Case of the Week 97

Blood smear from a febrile missionary who just returned from Nigeria. Diagnosis?

Sunday, December 13, 2009

Answer to Case 97

Answer: Plasmodium ovale (trophozoites)
Congratulations to everyone who wrote in with the answer - you all recognized the classic appearance of P. ovale in a thin smear of peripheral blood. Like P. vivax, P. ovale has prominent stippling (a.k.a. Schuffner's dots) and enlargement of the infected red blood cells, but the trophozoite forms are more compact than P. vivax, and many of the infected red blood cells (approximately 1/3) are elongated or oval in shape (hence the name ovale). In addition, one edge of the infected cells is often ragged or fimbriated. The characteristic features are outlined below:

Wednesday, December 9, 2009

Interesting PodCast

Here's an interesting podcast on how a lack of biodiversity might increase the rates of human disease, including malaria.

To hear the part of interest, fast forward to the 2 min, 22 second mark.

Monday, December 7, 2009

Case of the Week 96

The following was found on the scalp of a 60 year old woman. Identification?

Sunday, December 6, 2009

Answer to Case 96

Answer: Pediculus humanus, Human head or body louse.

Many of you were very observant and noticed that there was a similar image on my front page:

Thanks for writing in!