Monday, March 31, 2014

Answer to Case 298

Thank for all of the comments on my April Fool's Day hoax!

Some of my favorite identifications for this nasty looking 'parasite' are:
a "baby alien," "giant Ancylostoma duodenale" from a Sci Fi movie, and a "radiated tardigrade" (if you don't know what a tardigrade is, you should definitely look it up because they're really cool)

So the real answer is that this little guy is made out of clay.  You can buy him (and his kin) at:

I put him in water with food coloring.

Sunday, March 23, 2014

Case of the Week 297

A patient was noted to have rapidly increasing serum creatinine 4 months after receiving a renal allograft. A renal biopsy was performed, which revealed small oval/elongate objects within the renale tubules.  (CLICK ON IMAGES TO ENLARGE).  A variety of stains and additional studies were performed:
H&E, 200x
 H&E, 400x
 H&E, 1000x (note how tiny the structures inside the renal tubule cells are)
 The structures were partially acid fast (Ziehl Neelsen, 1000x)
 A Ryan's trichrome performed on tissue nicely highlighted the objects (1000x)
 A urine specimen stained with Ryan's trichrome also showed these structures.
By electron microscopy, the objects were seen within vacuoles in the renal tubular cells.
 Higher magnification by EM:

Saturday, March 22, 2014

Answer to Case 297

Answer: microsporidiosis

The images from the kidney show small oval spores (approximately 1.5 x 0.5 micrometers) within the renal tubular cells.  The fact that they are focally acid fast using Ziehl-Neelsen staining and nicely highlighted with Ryan's Trichrome Blue (a chromotrope 2R stain) is highly suggestive of microsporidiosis.  The positively-stained spores in urine are also consistent with microsporidia, although as Jamal points out, this is not a specific stain and other organisms such as yeasts can stain (although not usually as darkly red-pink as microsporidia spores).  Indeed, this can be a challenging stain to interpret, especially because many of the microsporidia (particularly those found in stool - Encephalitozoon intestinalis and Enterocytozoon bieneusi) are very tiny, measuring only 1 to 1.5 micrometers in length. Some of the other microsporidia (e.g. Nosema, Brachiola, Anncaliia) are significantly larger, measuring up to 5 micrometers in length and thus resemble small yeasts.

As many of the readers pointed out, it is the TEM image that provides confirmation of the diagnosis.  As noted by Dr. Louis Weiss, this is most likely Encephalitozoon cuniculi based on the clinical presentation and EM appearance (although he notes that other Encephalitozoon spp. will have a similar appearance on EM.)  We also performed PCR which was positive for E. cuniculi.  Some of the characteristic EM features are demonstrated below:

(note that Encephalitozoon cuniculi is not always present in a parasitophorous vacuole).

Interpreting TEM images of microsporidia spores can be tricky and expertise is limited to specialized settings such as the CDC.  When in doubt, I would contact them for assistance!

Monday, March 17, 2014

Case of the Week 296

The following case was generously donated by Florida Fan.  This object was seen while reading an iodine-stained fecal sediment at 400x (approximately 175 microns in diameter).  Identification?

Sunday, March 16, 2014

Answer to Case 296

Answer:  Not a human parasite, most likely plant material.

This case was generously donated by Florida Fan, who knew it wasn't a parasite but was hoping that someone would be able to identify this striking flower-like object.

I think that Tomáš Macháček has the answer.  He states " looks like some plant trichome which somehow contaminated food.  Compare it for example with Russian Silverberry trichomes ("  Looks like a very close match.  Thank you Tomáš for solving our mystery!

For those of you wondering, trichomes are a diverse array of appendages or outgrowths found on some plants.  Since we consume a wide variety of plant materials, it is no surprise that they are found occasionally in stool.

Monday, March 10, 2014

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)

Sunday, March 9, 2014

Answer to Case 295

Answer:  Uric acid crystals

This was a challenging case given that uric acid crystals are a very convincing mimic of Schistosoma hematobium eggs.  Fortunately they can be differentiated by a number of features:

  1. The crystals are pointed at both ends while S. hematobium eggs have a single (terminal) spine.
  2. The pointed ends of the crystals are more triangular, while true S. hematobium spines have a pinched-off appearance.
  3. Crystals are smaller than Schistosoma hematobium eggs (usually < 100 micrometers in length; compare their size to the surrounding epithelial cells) and vary significantly in size.  In contrast, S. hematobium eggs are large (112 - 170 x 40-70 micrometers).
  4. There are no internal staining structures on Papanicolaou stain, unlike what would be seen with true eggs (see example below).
  5. Crystals are often cracked, whereas true eggs rarely crack but instead may be crushed or deformed
  6. Crystals are very birefringent on polarized light unlike true eggs which do not polarize to this extent.
These features are demonstrated by the following images:

Comparison of true S. hematobium egg (left) and crystal (right) on Papanicolaou stain:

Uric acid crystals may be seen in urine in a number of settings, particularly in acidic urine and certain metabolic states such as gout.  

From Blaine Mathison:

These ellipsoid-shaped structures might look like schisto
but really they're uric acid crystals, dont ya know
high concentrations in blood might lead to gout
so from your diet leave excess sugars out

or excruciating pain you may feel down in your toe!

Monday, March 3, 2014

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?

Sunday, March 2, 2014

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 (  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