Case of the Week 197

The following were sent in a stool ova and parasite transport media for identification. The objects were found in the stool of a 4 year old child. They measure approximately 3 mm in length.

What is your differential diagnosis?
What would be the next steps for confirming an identification?

Answer to Case 197

Answer: Consistent with Dipylidium caninum proglottids.

These small white-tan proglottids can appear as "grains of rice" and "cucumber seeds." They are often noted by the caregiver in the patients stool (usually a young child) due to their motility. I've shown various examples of D. caninum proglottids in previous cases, which demonstrate the size and mild variability in shape that may be observed:

Case 188 shows a nice example of "rice grain" morphology while
Case 107 shows a more characteristic appearance of a "cucumber seed"

In order to confirm the diagnosis, the proglottids should be manipulated to express eggs for examination. The fluid or stool submitted with the proglottids should also be examined for eggs. Examples of characteristic eggs can be seen in both of the cases above. In rare cases when eggs are not forthcoming, the proglottids can undergo histologic sectioning.

Case of the Week 196

The following was seen inside a plastic 'ziplock' style bag sent in for parasite identification. The source was "skin scrapings." Thankfully, the bag was handled with care and not opened prior to being examined under the dissecting microscope. The appendages of these objects were still moving. Interestingly, there was no obvious skin flakes in the bag.

Identification? (CLICK ON IMAGES TO ENLARGE)

Answer to Case 196

Answer: Mite, not Sarcoptes scabiei/scabies mite

While the appearance of this mite is very similar to the human scabies mite, there are subtle differences that allow it to be differentiated from Sarcoptes scabiei:

1. This mite has more pronounced spines or 'hairs'
2. The appendages are longer
3. The size is slightly bigger (approx 1 mm in length) although I didn't provide the size for this case (my mistake!)

The following photo demonstrates these morphologic differences between the 2 mites (mites are not shown to scale)


A previous case of the week shows a crusted scabies infection in which adult mites were seen under the dissecting microscope. Note the differences in appearance to the mites shown in this current case.

This case was challenging because the history was suggestive of scabies. However, it is important to remember that numerous bird and other animal mites can bite humans and transiently be found on human skin. The fact that there were no skin flakes in the bag along with the mites was suggestive that these mites weren't actually burrowing in human skin.

Case of the Week 195

A 30 yo man with travel to South America presented with chronic non-healing warty skin lesions. Repeated skin biopsies were negative for microorganisms by histopathology but culture using brain-heart infusion media with rabbit blood grew the following on day 12 of incubation at 25C.

(1000x original magnification)


(1000x original magnification, Giemsa)



Diagnosis?

Answer to Case 195

Answer: promastigotes of Leishmania species.

Thank you for everyone who wrote in with an answer for this case. Most of you recognized that this is the motile form (promastigote) of Leishmania, which grows in culture at 25C and is the stage found in the sandfly vector. As noted by anonymous, the faint big dark pink blob is the nucleus and the small clear pink dot is the kinetoplast:


The 'warty' appearance of the lesions was a bit atypical compared to the classic ulcerative leishmanial lesion, but the chronic nature of the lesions and history of travel to South America fit well with the diagnosis of leishmaniasis. I reviewed all of the skin biopsies from this case and *maybe* saw a few amastigotes, but the overall appearance was nothing like the classic histopathology that I am used to seeing. The dermatologists have hypothesized that the lack of amastigotes in the skin biopsies may be due to an unusual immune response associated with the proliferative warty nature of the lesions.

The CDC is currently performing PCR to speciate the organism, but based on the smaller size of the promastigotes in culture, think it is most likely to be L. braziliensis or L. (Viannia) panamensis. Both of these are agents of cutaneous and mucocutaneous leishmaniasis, so the patient will most likely be treated with a systemic therapy such as liposomal Amphotericin B or (more likely) the pentavalent antimonial Pentostam (sodium stibogluconate).

Case of the Week 194

A corneal biopsy was obtained from a man with corneal opacities and painful erosions. He had not been able to wear his contact lenses for over 1 month due to the pain. (CLICK ON IMAGES TO ENLARGE)

H&E, 40 x original magnification


H&E, 100x original magnification


H&E, 400x original magnification



The corneal biopsy was also cultured in a peptone-
yeast extract-glucose broth and the following were identified.


Diagnosis?

Answer to Case 194

Answer: Acanthamoebic keratitis

Note the multiple cysts within the corneal stroma.


Characteristics cysts and trophozoites are seen in the following image:


Culture of the corneal biopsy grew organisms morphologically consistent with Acanthamoeba species, including trophozoites with spinous processes and wrinkled cysts.