Monday, April 14, 2014

Case of the Week 300

Dear group,
We are now on our 300th case! This blog was 'born' in 2007 as a way for me to share cases with just a few clinical microbiology fellows at my institution.  I am now very proud (and amazed) to say that this blog has expanded to have an international viewership and receives more than 14,000 page hits each month from individuals with a wide variety of backgrounds and interests.  Your readership and comments continue to inspire me.  Thank you!

The case for this week consists of several strands of hair from an elderly man living in a skilled nursing facility.  What is your identification?

Monday, April 7, 2014

Case of the Week 299

The following object was noted in a routine endocervical Papanicolaou-stained smear.  Identification?  How would you sign this case out?  This case was generously donated by Tony Rollins CT(ASCP) and Dr. Harvey Cramer, MD.

Sunday, April 6, 2014

Answer to Case 299

Answer:  Not a human parasite.

This is an incidental finding of a free-living plant/water nematode that likely contaminated the specimen during collection, transport, or staining.  If this had been my case, I probably wouldn't even make mention of the nematode in the actual patient report to avoid unnecessarily raising concerns for the clinician or patient.

If this been a more significant problem (e.g. there had been a lot of these worms present), then I would have taken additional steps such as examining the reagents used in my lab and having a discussion with the clinician about what the patient might have using (e.g. naturopathic douches) that could have introduced the worms into this location.

Many of you wrote in with some good suggestions of what this worm could be, including a variety of human parasites that have similar morphologic features or could conceivably end up in an endocervical location. However, these parasites can be ruled out based on their larger size and lack of expected features (e.g. no narrow anterior end for Trichuris trichiura or no thin pointed tail for a female Enterobius vermicularis. I think that the most challenging worm to rule out was an anisakid (Anisakis sp. or Pseudoterranova decipiens) based on what appeared to be a posterior mucron (see below).  However, this is a look-alike; the structure we are seeing is actually a stylet at the anterior end of the worm, which may be seen in a variety of free-living nematodes. Fortunately size is a helpful differentiating feature; the worm in this case is less than 300 micrometers in length while anisakid larvae are 20 to 35 millimeters in length.

Thank you all for writing in on this case!

Tuesday, April 1, 2014

Case of the Week 298

The following was submitted for parasite identification.  The source of the specimen is "found in stool"

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!