Tuesday, February 28, 2017

Case of the Week 436

This week's case was generously donated by Dr. Sabarinathan from Madras Medical College in Chennai, India. The patient is a young man with a 2-week history of epigastric pain and vomiting. Physical examination was normal, and a complete blood count showed only a mild anemia (hemoglobin of 9.8 g/dL). An ultrasound of the abdomen was normal and so an upper gastrointestinal endoscopy was performed. This is what was seen:

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 18, 2017

Answer to Case 435

Wow, this case generated a lot of interest, with requests for the answer when I didn't post yesterday. My apologies for leaving you all hanging!

This is a case of a non-parasitic fiber that had been transcutaneously implanted and migrated under the skin due to physical pressure (i.e. walking). Although the presentation was suggestive of a cutaneous parasitic infection such as cutaneous larva migrans (CLM), the length of the object and dark color were not consistent with any human or zoonotic parasite. Several readers pointed out specifically that the larvae that cause CLM are microscopic and therefore would not be visible to the naked eye. Also, the path formed by a migrating worm would be more serpiginous rather than the semi-lunar pattern observed here. Other subcutaneous or intra-epidermal/dermal worms such as Loa loa, zoonotic microfilariae, and Dracunculus medinensis were also suggested but rightly discarded by readers because of the size and color of this object. There is no parasite, to my knowledge, that would have this appearance and be present in this location in human skin.

One intriguing suggestion was that this was cutaneous pili migrans (CPM) - an excellent thought. CPM is a phenomenon in which a hair grows within the skin rather than up and out of the skin, and is seen as long dark object just below the skin's surface. This is most common on hair-bearing regions of the body and would be unusual on the sole of the foot. However, removal of the object would be required to rule out  CPM. Therefore, this is exactly what we did. Here are photographs of the object that we removed (cut in half):

As you can see, it looks to be a synthetic fiber and not any type of worm. It was extremely resilient, and while bendable, did not easily break. Just for fun (and because I knew you would all want to know), we analyzed the fiber using infrared spectrum analysis, which showed it to be most consistent with azlon, a synthetic fiber commonly used to make clothing and household objects.

Thanks again to Emily Hall for donating this fascinating case!

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.