Case of the week 295

The following were seen in a Papanicolaou-stained urine specimen from a 53 year old woman with chronic dysuria.  She has no recent travel history outside of the U.S., but had been to parts of sub-Saharan Africa over 10 years ago. Images are shown at 400x magnification.  Identification?

 
 

(with polarized light microscopy)

Case of the Week 294

The following were seen in a stool ova and parasite exam in a 34 year old businessman with recent travel to India.  He reports a 2-week history of watery diarrhea.  They are relatively few in number and range in size from 8 to 20 micrometers in diameter.  How would you interpret this finding?

Answer to Case 294

Answer:  Blastocystis hominis

Thanks to everyone who wrote in with the response - you were all correct.  Blastocystis is most commonly present in stool as cysts (vacuolated forms/central-body forms) which contain a large central body similar to a vacuole and up to 4 peripheral nuclei.  As mentioned by Florida Fan, they range in size from 5 to 20 (or even 30) micrometers in diameter, although the usual range is 8-10 micrometers.

There were a number of comments/questions about the Blastocystis subtype and how that might be linked to the patient's symptoms. At this time, the role of this protozoan parasite as a human pathogen is somewhat controversial, but it does seem that certain subtypes are more common and may be associated with clinical symptoms.  Therefore, the general trend in the U.S. is to treat symptomatic patients when no other cause of symptoms is found.  In this case, numerous stool exams did not reveal any other parasites and the patient was treated with metronidazole with some improvement. Unfortunately we don't know the subtype of this infection since that testing is not readily available for clinical laboratories.

For those of you who are interested in learning more about Blastocystis, I highly recommend the blog by Christen Run Stensvold (http://www.blastocystis.net).  He regularly highlights new literature on this organism and discusses facets of this parasite's biology in much more detail than I could!

And now a poem by Blaine Mathison:

Blastocystis is such the taxonomic conundrum

spinning protozoologists around 'til their minds go numb

among the amoebae it's called its home

even as an alga it's once been known

but now a stramenopile, 'til what other theories may come

Case of the Week 293

Several hairs from the groin region of a 24 year old male were submitted to the Clinical Parasitology lab for examination.  One hair contained the following structure cemented onto the hair shaft.  It measures approximately 2 mm in length.  Identification?

Answer to Case 293

Answer:  nit (egg) of Pthirus pubis, the crab louse

You can differentiate this nit from the similarly appearing nits of the head and body lice by its taller operculum (cone of cells at the apex):

And now a poem from Blaine Mathison (I'm not taking responsibility for this one!)

Chilling at home in his bachelor pad

trying to get all the booty that he could grab

but his latest of trysts

gave him a gift that persists

for now he's host to Sebastian the 'Crab'

Case of the Week 292

The following is a skin biopsy from an ulcerating lesion on the left thigh of a 70 year old woman.  She is being treated with chemotherapy for diffuse large B cell lymphoma.

Hematoxylin and Eosin (H&E), 20x magnification 

H&E, 40x

H&E, 400x

H&E, 400x

H&E, 1000x

Gomori Methenamine Silver (GMS), 1000x

Answer to Case 292

Answer:  Trophozoites and Cysts of Acanthamoeba species/Balamuthia mandrillaris 

A multiplex PCR for free-living amebae was also performed on this tissue, which was positive for Acanthamoeba sp. DNA.

Many of you noted that the organism morphology is characteristic for Acanthamoeba/Balamuthia (it is nearly impossible to tell the 2 apart by light microscopy, so I group them together) but mentioned that the skin is an unusual location for these organisms.  It is correct that we don't usually see the free-living amebae in the skin.  However, if you take a look at the CDC life cycle of Acanthamoeba and B. mandrillaris, you'll note that one port of entry to the blood stream (and eventually the brain) is broken skin.  Therefore, it is essential to identify amebae in skin biopsies so that treatment can be implemented before dissemination occurs.  In this case, note how the organisms are clustered around blood vessels, indicating their potential for hematogenous dissemination!  Fortunately this patient did not have evidence of brain involvement.