Sunday, February 19, 2017

Case of the Week 435

This week's challenging case was donated by Dr. Emily Hall. The patient is a previously-healthy toddler who began acting unusually fussy and refused to ambulate. Examination reviewed a thin black object under the skin of her right foot. Extraction was unsuccessful and the child was playing and ambulating at the end of the visit and was therefore sent home. The child was brought back the following day because the object had moved approximately 3 cm within a 24 hour period in the semilunar pattern shown in the image below:
At this point, the object was removed and sent to the parasitology lab. Rather than showing you the images of the object that was extracted, I thought I would ask for your diagnosis based on the clinical image alone. I will show you the images and provide the diagnosis next week!

The image is shown with permission from the mother.

Saturday, February 11, 2017

Case of the Week 434

This week's case is another simple identification. The following structures were seen in stool of a young child.

What are these structures?

Friday, February 10, 2017

Answer to Case 434

Answer: Enterobius vermicularis (pinworm) eggs

Note the characteristic features including the thin colorless shell and partially-oval shape that is flattened on one side. The larvae are not fully developed within these eggs, but generally are developed (and infective) within 4-6 hours of the eggs being laid.
This was an interesting case in that the eggs were seen in stool rather on a peri-anal adhesive tape preparation. The latter is the preferred method for detecting pinworm eggs since the adult female lays her eggs on the perianal skin folds. However, eggs may attach to the stool as it passes through the anus, and are therefore occasionally (but not reliably!) seen using the ova and parasite exam.

Sunday, February 5, 2017

Case of the Week 433

This week's images were generously donated by Florida Fan. The following structures were seen in a concentrated stool specimen and measured approximately 75 micrometers in greatest dimension (2.5 micrometers per line on the scale bar). Identification?

Saturday, February 4, 2017

Answer to Case 433

Answer: Hymenolepis diminuta, the rat tapeworm. Humans become infected when accidentally ingesting infected arthropods.

H. diminuta eggs can be differentiated from the similar-appearing eggs of Hymenolepis nana by their larger size (70-80 micrometers in greatest dimension) and lack of polar filaments. In contrast, H. nana eggs are 30-50 micrometers in greatest dimension and have polar filaments radiating out from the inner shell. Both eggs have an inner shell surrounding the 6-hooked onchosphere and an outer shell.

Here are some of the defining features of H. diminuta eggs:

Monday, January 30, 2017

Case of the Week 432

This week's case was generously donated by Dr. Nicole Hubbard. Small white motile objects were seen in a infant's stool specimen by the mother and a stool ova and parasite exam was ordered. The results of the stool exam were negative however, and objects continued to be seen; therefore representative objects were placed in formalin and sent to the laboratory for identification. They measured approximately 12 mm in greatest dimension. By manipulating the objects with forceps, the following structures were identified:

4x objective
10x objective
 40x objective


Sunday, January 29, 2017

Answer to Case 432

Answer: Dipylidium caninum egg packets

Thank you to all of my readers who wrote in with the answer - you all recognized the very characteristic appearance of the eggs within packets. This appearance, along with the case presentation and description, is classic for infection with D. caninum. 

Because the proglottids of D. caninum are so small (resembling grains of rice), they can be difficult to definitively identify in the parasitology lab. To make matters worse, they are often dried out or partially mangled when they arrive. Therefore, we will rehydrate the specimen in saline when needed, and then view them under the dissecting microscope. With some gentle manipulation using forceps, we can usually express egg packets out of the proglottids. This is what we did in this case and explains why the eggs packets are slightly immature appearing, without clearly visible internal hooklets. Here are some images from this case with further detail.

If that fails, proglottids can also be cleared using lactophenol and mounted on a slide.

Saturday, January 21, 2017

Case of the Week 431

This week's case is an arthropod which was found on a sandy beach in South America. It is approximately 1 mm in greatest dimension.


Friday, January 20, 2017

Answer to Case 431

Answer: Tunga penetrans adult flea

This was a tricky case because this flea is rarely seen outside of the human host. When it comes to clinical attention, it is usually because the female has embedded in the skin and has enlarged (with eggs), causing a painful lesion on the host.

When seen, this flea can be differentiated from other common human-biting fleas by a few characteristic features, including a shorter, rounder body, long serrated mouthparts, and compressed thoracic region. It does not have genal or pronotal combs. I've shown a Ctenocephalides adult below for comparison.
Florida Fan invited us to walk on his beautiful Florida beaches where he guarantees we will NOT encounter Tunga penetrans!

Saturday, January 14, 2017

Case of the Week 430

This week's case is from an elderly institutionalized patient with diffuse thickened skin on her arms and back. A crust from skin was submitted for examination, and scrapings showed the following:

Many were hard to photograph because they kept moving! Identification?