Sunday, November 25, 2012

Case of the Week 234

A large "worm" (several cm in length) was passed in the stool of a 4-year old boy.  Unfortunately, rather than being submitted intact to the microbiology laboratory, it was sent to surgical pathology where slides containing serial cross-sections were produced.  Below are representative H&E images taken at 40 and 100 times original magnification:


Saturday, November 24, 2012

Answer to Case 234

Answer:  Earthworm

Given the larger size of this worm, Ascaris lumbricoides would be at the top of my differential.  However, note that this worm does not contain a thick acellular cuticle and a layer of tall circumferential muscle cells as would be expected for this nematode.  Instead, note that the outer cuticle is very thin and is underlain by tall epithelial cells containing mucin-producing cells. Below the epithelial layer are longitudinal and circumferential muscle cells, creating a thick muscular layer.

Finally, earthworms have a characteristic thickened band that is present near the anterior end of the worm called the clitellum.  Fortunately we were able to capture a cross-section through the clitellum as shown below.

Of course, this worm could have been most easily identified if it had been submitted to the microbiology lab immediately, before it was sectioned, fixed, and embedded.  I think Hans says it best with "Pathology, stay away from our worms!"

As to how this worm got into the boy's stool, I don't know if it was swallowed (would it survive the GI tract?  Any volunteers to find out?) or ended up in the stool after it was passed. 

Tuesday, November 20, 2012

Case of the Week 233

A 67 year old contact lens wearer with eye pain was found to have a corneal ulcer. Corneal scrapings (unstained wet prep) revealed the following (CLICK ON IMAGES TO ENLARGE).  The rounded structures measure approximately 15 micrometers in diameter.

This case was generously donated by Dr. Julie Ribes.

Monday, November 19, 2012

Answer to 233

Answer:  Cysts of Acanthamoeba sp.

These cysts have a very characteristic appearance, being uninucleat, usually between 10-25 ┬Ám in diameter, and possessing a wrinkled outer wall (exocyst) and hexagonal, polygonal, star-shaped, or spherical inner wall (endocyst).

Monday, November 12, 2012

Case of the Week 232

The following 17 mm x 9 mm skin ellipse  was received in the Clinical Parasitology lab for identification. The container was marked "rule out retained tick mouth parts."

On closer examination, the center of the ellipse contained  a dark irregular object:

Through careful dissection, I was finally able to extract the following: 

If you had received a phone call on how to best remove this object, what would have been your advice?

Sunday, November 11, 2012

Answer to 232

Answer:  Retained tick mouthparts: toothed hypostome and part of the basis capituli.  Unfortunately, it is not possible to definitively identify the genus of the tick from the parts available.

The answer to the second question is more interesting:  If you had received a phone call on how to best remove this object, what would have been your advice?

Most of you correctly responded that the best way to remove a tick is by the use of forceps.  The CDC has an excellent web page with instructions for removing ticks that you can access HERE.  Excision is not necessary (!) unless the tick is not readily recognized (I've seen an engorged tick mistaken as an infarcted skin tag).  In certain situations, retained mouthparts might also be difficult to remove without excising the surrounding skin, although the excised tissue does not need to be large.
In this case, the diagnosis (retained tick mouthparts) was only suspected which may explain why such a large excision was performed. 

Monday, November 5, 2012

Case of the Week 231

A 40 year old woman retrieved a 'worm' from her nasal cavity and brought it to her primary care physician, who then submitted it to the laboratory for identification.  The following images show the specimen that was received (pressed between 2 glass slides). (CLICK ON IMAGES TO ENLARGE)

40 times original magnification, unstained

100 times original magnification, unstained

200 times original magnification, unstained

400 times original magnification, unstained 

400 times original magnification, unstained

400 times original magnification, unstained

Identification?  How would you sign this case out?

Sunday, November 4, 2012

Answer to Case 231

Answer:  Arthropod, not a human parasite. The spine-like structures seem to bit best with an adult insect.  As Florida Fan said, "This seems like a 'flown in' case!"

Thank you for all of the comments on what the differential for "worm in nose" is.  The main one is nasal myiasis, although the morphologic features would be very different than what is seen in this case. You can check out a previous case of myiasis involving the ear HERE.