Monday, December 24, 2012

Case of the Week 238

Can anyone identify the Holiday arthropod?

Sunday, December 23, 2012

Answer to Case 238

Answer:  Pediculus humanus

As pointed out by Hans, P. humanus has 2 ecotypes, which are referred to as head lice and body lice.  Although they are very similar and have overlapping body features, they differ by only a single gene and can successfully interbreed to produce fertile off-spring.  Here is an interesting review on human head and body lice which covers the taxonomy in greater detail:

Veracx and Raoult. Biology and genetics of human head and body lice. Trends in Parasitology, December 2012, Vol. 28, No. 12.

Enjoy, and Happy 2013!

Monday, December 17, 2012

Case of the Week 237

The following were seen in a concentrated stool wet preparation that had been stored in formalin for 6 months. They measure approximately 60 micrometers in greates dimension.  Identification?

Sunday, December 16, 2012

Answer to Case 237

Answer:  Ascaris lumbricoides ova (embyronated)

Monday, December 10, 2012

Case of the week 236

The following were observed in skin scrapings from a 75 year old man with an itchy rash.


Unstained, 100 times original magnification

Unstained, 400 times original magnification

Unstained, 400 times original magnification (focal plane 1)

Unstained, 400 times original magnification (focal plane 2; note appendages)

Unstained, 400 times original magnification (focal plane 3)

Sunday, December 9, 2012

Answer to Case 236

Answer:  Scabies mites (Sarcoptes scabiei)

Note that the specimen shown appears to have 6 legs, indicating that it is a nymph.  Like all other acari (inc. ticks and mites), the adult will have 8 legs.

I like this case in that you can clearly see the features of the developing nymph inside the egg. 

You can also appreciate the short stumpy legs terminating in spines.

Monday, December 3, 2012

Case of the Week 235

This week's case is a bit challenging.

The following objects were seen in a Papanicolaou-stained endocervical preparation by the screening cytologist and brought to the microbiology lab for identification.  They measure approximately 8-10 micrometers in diameter.  The woman is asymptomatic.  (shown at 1000 times original magnification)



Sunday, December 2, 2012

Answer to Case 235

Answer:  Presumed amebae; either non-pathogenic amebae from GI contamination or possible free-living organisms.

I posted this case because it was challenging for me as well and I wanted to see what the others had to say.  Of the comments I received, the votes were as follows:

Amebae, (various types) - 8 votes
Chlamydia-infected epithelial cells - 1 vote
White blood cell, NOS - 1 vote
Trichomonas vaginalis - 2 votes

I was happy to see that the consensus supported my initial diagnosis.  The features that I feel support the identification of ameba include the small size (< 10 microns in diameter), small nucleus (smaller than would be expected for an epithelial cell or macrophage) with large nucleolus/karyosome, and what appears to be phagocytosed material in the cytoplasm:

Thank you for writing in with your comments!