Monday, July 28, 2008

Case of the Week 31

Specimen: Fluid Aspirated from a lung cyst.

Answer to Case 31

Answer: Echinococcus spp. hooklets. It is common for protoscoleces (the larval form of echinococcus) to degenerate, releasing free hooks and cellular debris into the cyst fluid. This material comprises the 'hydatid sand' or gritty material in aspirated cyst contents. Note the characteristic shape and refractile nature of the hooklets.

The differential diagnosis includes hooklets from a cysticerca (larval form of Taenia solium) which are very similar in appearance to the hooklets of Echinococcus spp. However, a cysticerca contains only one larva which does not commonly degenerate and release its hooklets. Also, the size of the cysticerca cyst is much smaller than that of echinococcus and contains very little fluid, making aspiration impractical.

Sunday, July 20, 2008

Case of the Week 30

The two adult worms in this histologic section are within a mesenteric vein.
Identification (genus only)?

While only shown as a low-power, low resolution image, there are several features present that should allow you to identify the worms.

Saturday, July 19, 2008

Answer to Case 30

Answer: Adult Schistosome worms. They are shown in cross section at a level where they are not in copula. However, if you were to take sections along the entire length of the worms, you would most likely see the female resting within the male's ventral gynecophoral canal.

Features for identification:
First, the location within a blood vessel and that fact that I told you these are 2 adult worms are big clues. The other important feature to note is that they are flatworms (i.e. trematodes or flukes). If you were to uncurl the edges of the male, you would see that it is fairly flat in cross-section. The schistosomes are the only blood flukes, and therefore, the only flatworms that you would see within a blood vessel. Your other main differential would be the adult filarial worms Wucheria and Brugia spp. They may also be found within vessels (lymphatics) but they are nematodes - round worms (i.e. their body is round on cross-section).

Also, bonus points to Alasdair who identified these worms as S. mansoni. The males of this species have conspicuous tuberculations which are useful from distinguishing it from the smooth-tegumented S. japonicum.

Sunday, July 13, 2008

Case of the Week 30

Here's a nice fun one. These eggs are approximately 50-60 microns in length. Identification? What is the best specimen to find these eggs?

Saturday, July 12, 2008

Answer to Case 30

These are eggs of Enterobius vermicularis (a.k.a. Pinworm). Although they may be seen occasionally in stool samples, the best way to identify them is by applying the sticky side of clear (non-frosted) cellophane tape to the anal region and then examining the tape under a microscope. That's what is shown here. The eggs are quite distinctive: clear, oval shaped, 50-60 microns in length, and flattened on one site.

My thanks to anonymous who gave me a new word for 'anus'.

Sunday, July 6, 2008

Case of the Week 29

This tiny adult worm can cause serious life-threatening disease. Identification? Where would you expect to find the adult and larval forms? CLICK ON IMAGES TO ENLARGE.

Answer to Case 29

Answer: Echinococcus spp. adult worm. This small adult tapeworm is found in the intestine of canines - never humans. The eggs are released into the environment with the feces and normally infect herbivores such as sheep (E. granulosus) and rodents (E. multilocularis). When humans are unfortunate enough to ingest these eggs, they develop the cystic larval form in the liver and other organs. The larval stage is referred to hydatid disease and can be life-threatening since the cysts can attain large sizes, impinge on neighboring structures, and even rupture, releasing large amounts of anaphylaxis-inducing antigens.

Thank you to Alasdair who wrote in from The
Gambia to answer this week's case! (Now that's dedication).